Robert Johns | 20 Dec, 2023

Float vs Double Data Types: What's The Difference [Updated]


In this article, I’m going to explore the classic programming topic of float vs double.

Whether you’re brand new to coding or a seasoned pro, how well do you really know float and double data types?

Read on to find out!

I’m going to cover what floating-point numbers are, the difference between float and double, how to use them in common languages, pitfalls to watch out for, and tips for how to choose between float and double for different types of real-world applications.

At a time when the Bureau of Labor and Statistics reports an average salary of over $100K for programmers, fundamental skills like understanding float vs double can be the first step to a rewarding career!

So, if you’re ready, let’s dive in and learn about float vs double!

What Are Floating Point Numbers?

Before we explore the difference between a float and a double, let's dive into the concept of floating-point numbers in general. Hopefully, if you've taken any form of programming course, these concepts will be somewhat familiar to you.

If you've ever worked with numbers in programming, you've likely encountered these. They're one of the go-to data types in every programmer's toolkit, as they're versatile and essential for handling a range of numerical values.

But what are floating-point numbers?

Floating-point numbers are a way to represent real numbers in programming, which allows us to work with a wide range of values, from incredibly small to immensely large.

This means that a floating-point number can represent both fractional and whole values with varying degrees of precision, while its cousin, the integer, can only represent whole numbers without any fractional component.

But why are they called 'floating-point' numbers? This is because the decimal point can 'float'; it can be placed anywhere relative to the significant digits of the number.

It's this flexibility that makes them so useful for programming.

The concept of a floating point number isn't new, and in fact, it's been around since the early days of computing, though constantly evolving with our need for more precise and varied numerical computations.

The main idea is to represent numbers in a way that can accommodate both very large and very small values, something that's crucial in fields like scientific computing, graphics processing, and financial analysis.

Now, if you're new to programming, you might have wondered, why not just use integers instead of the type float?

Well, integers are great for counting or when precision is not a concern, but they fall short in situations requiring decimal values with fractional values and decimal digits.

Think about scientific calculations, currency conversions, or even something as simple as measuring weight or length. Floating-point numbers allow us to handle these scenarios more effectively.

In most programming languages, we represent floating-point numbers with a standard format that was defined by the IEEE (Institute of Electrical and Electronics Engineers).

This format ensures consistency across different systems and languages and also makes it easier to work with floating-point arithmetic reliably.

So, there you have it — a quick primer on floating-point numbers. They're a fundamental part of programming, enabling us to work with a vast range of numeric values with ease.

Whether you're calculating the trajectory of a spaceship or just balancing your checkbook, floating-point numbers are your go-to tool for precision and versatility in the numerical world.

Now, let's check out the two most commonly used floating-point numbers, the aptly named Float and its brother, the Double.

Float vs Double: What's The Difference?

Now we've got a handle on floating-point numbers, let's zoom in on two specific types that you'll frequently encounter in programming: the float data type and the double data type.

At first glance, these can seem similar, but there are some important differences you need to be aware of.

Let's start by defining both types in the general sense:

  1. Float: Short for "floating point," this type stores single-precision floating-point numbers. It's fast and efficient for most tasks and typically occupies 32 bits (or 4 bytes) in memory, which dictates its precision and the range of values it can represent.
  2. Double: This is short for "double precision." As the name suggests, double variables are all about doubling down on precision. They take up 64 bits in memory, allowing them to represent numbers with a greater range and more precision.

Great, now, let's look at the key differences between float variables and doubles:

  • Digits of Precision: This is the main difference. Float precision is less precise than double precision. This all comes down to the number of digits each type can accurately represent. With a Float, you might start losing precision after six or seven decimal places, while a Double can handle about 15 decimal places.
  • Memory Usage: As I mentioned, Floats are typically 32 bits and require less storage, while Doubles are 64 bits. This affects not just precision but also how much memory your program uses.
  • Range of Values: Doubles can handle a wider range of values because of their size, which makes them really useful in scenarios where the magnitude of the values can vary greatly.

Now, this is the main question: how do you choose which one to use?

I remember when I was first starting out in coding, and in particular with C++, I started choosing to use Doubles instead of Floats because I felt that more precision could only be a good thing. But, like most newcomers to programming, I didn't fully grasp the idea that there is a time and a place to switch between a Float and a Double.

This leads me to my main point: when you need to choose between a Float and a Double, you need to consider your application's needs.

For example, If you need to conserve memory and your calculations don't require extreme precision, Floats might be sufficient.

Then again, for applications where precision is crucial, like scientific calculations or complex algorithms, the Double may be the better choice.

In the following sections, we'll see how different programming languages implement these data types, and we'll also look at some code examples to better understand their usage in real-world scenarios.

I will say this, keep in mind that the choice between Floats and Doubles can significantly impact the accuracy and efficiency of your program, so it's a decision worth pondering over!

How Different Languages Utilize Float and Double

When it comes to the float and double, different programming languages have unique ways of handling these data types.

Let's take a quick tour to see how some of the most popular languages use float and double.

C and C++

  • In C and C++, float and double represent floating-point numbers with different precision levels, which you should learn from any good C or C++ course.
  • A float is a single precision, 32-bit representation of a floating point number, while a double provides double precision, occupying 64 bits.
  • C++ also introduces long double, offering even more precision, though its size and precision vary by system.


  • The Java float follows a similar approach to C-type languages, with the float being 32-bit and the double 64-bit floating-point.
  • Java programs have strict adherence to IEEE standards for floating-point arithmetic, which means that the behavior of float and double is predictable and consistent across platforms.


  • C# offers both float (32bit) and double (64bit) types for different levels of precision.
  • It's similar to Java in its adherence to IEEE standards, ensuring consistent behavior across different systems.


  • Python takes a slightly different approach. It only has one floating-point type, float, implemented as double precision (64bit) in C.
  • This simplification means you don't usually need to choose between single and double precision, which is why dealing with numbers is so easy on a Python course.


  • JavaScript is unique in that it doesn't explicitly define float and double. It has a single Number type, a 64-bit floating point (like double).
  • For specific applications, JavaScript offers Typed Arrays, such as Float32Array and Float64Array, which can be analogous to float and double.

Swift, Kotlin, Go, and Rust

  • These newer languages also provide distinct types of float and double.
  • Swift and Kotlin, for instance, have Float and Double, mirroring the precision levels of 32-bit and 64-bit floating-point types.
  • Go uses float32 and float64, and Rust uses f32 and f64, again corresponding to 32bit and 64bit precision.

In each of these languages, the choice between float and double depends on the needs of your application, particularly in terms of precision and memory usage.

If you want a quick reference guide to help you remember this key information, check out the table I've added below. Now, in the next section, I'll take a look at some code examples to see how these types are used in practice.

Language Type Precision Memory Usage Range (Approx.) Default Type Special Values Supported
C/C++ Float Single-precision (7 decimal digits) 32 bits 1.2E-38 to 3.4E+38 Double Yes (NaN, Inf)
  Double Double-precision (15 decimal digits) 64 bits 2.3E-308 to 1.7E+308 Double Yes (NaN, Inf)
Java Float Single-precision (7 decimal digits) 32 bits 1.4E-45 to 3.4E+38 Double Yes (NaN, Inf)
  Double Double-precision (15 decimal digits) 64 bits 4.9E-324 to 1.7E+308 Double Yes (NaN, Inf)
Python Float Double-precision (15 decimal digits) 64 bits 2.2E-308 to 1.7E+308 Float Yes (NaN, Inf)
JavaScript Number Double-precision (15 decimal digits) 64 bits 5E-324 to 1.7E+308 Number Yes (NaN, Inf, -0)
C# Float Single-precision (7 decimal digits) 32 bits 1.5E-45 to 3.4E+38 Double Yes (NaN, Inf)
  Double Double-precision (15 decimal digits) 64 bits 5.0E-324 to 1.7E+308 Double Yes (NaN, Inf)
Swift Float Single-precision (7 decimal digits) 32 bits 1.2E-38 to 3.4E+38 Double Yes (NaN, Inf)
  Double Double-precision (15 decimal digits) 64 bits 2.3E-308 to 1.7E+308 Double Yes (NaN, Inf)
Kotlin Float Single-precision (7 decimal digits) 32 bits 1.4E-45 to 3.4E+38 Double Yes (NaN, Inf)
  Double Double-precision (15 decimal digits) 64 bits 4.9E-324 to 1.7E+308 Double Yes (NaN, Inf)
Go float32 Single-precision (7 decimal digits) 32 bits 1.4E-45 to 3.4E+38 float64 Yes (NaN, Inf)
  float64 Double-precision (15 decimal digits) 64 bits 4.9E-324 to 1.7E+308 float64 Yes (NaN, Inf)
Rust f32 Single-precision (7 decimal digits) 32 bits 1.2E-38 to 3.4E+38 f64 Yes (NaN, Inf)
  f64 Double-precision (15 decimal digits) 64 bits 2.2E-308 to 1.7E+308 f64 Yes (NaN, Inf)

Code Examples With Float and Double

To illustrate the practical differences between float and double, I've put together some code examples in various programming languages.

The idea here is to demonstrate how each type is declared and used and the impact of their precision in calculations.

C/C++ Example

#include <stdio.h>

int main() {
    float floatValue = 3.14159265358979323846;   // Single-precision
    double doubleValue = 3.14159265358979323846; // Double-precision

    printf("Float value: %.7f\n", floatValue);
    printf("Double value: %.15f\n", doubleValue);

    return 0;

Explanation: This C code declares a float and a double, each initialized with Pi to many decimal places. The printf function demonstrates the difference in precision: float cuts off after 7 decimal places, while double goes much further.

Java Example

public class Main {
    public static void main(String[] args) {
        float floatValue = 3.1415927f;   // Note the 'f' suffix for float
        double doubleValue = 3.141592653589793;

        System.out.println("Float value: " + floatValue);
        System.out.println("Double value: " + doubleValue);

Explanation: This is very similar to our C example, but of course it's in Java. Notice how I've f suffix to explicitly define a float literal in Java. If this is unfamiliar to you, consider a Java course to refresh your skills with numeric types.

Python Example

floatValue = 3.14159265358979323846  # Python's float is a double-precision

print("Float value:", floatValue)

Explanation: Python only has one floating-point type (float), which is actually a double-precision floating-point number. This example shows Python's handling of a floating-point number with many decimal places.

JavaScript Example

let floatValue = 3.14159265358979323846;   // JavaScript uses double-precision for Numbers

console.log("Float value:", floatValue.toFixed(7)); // Limiting to 7 decimals
console.log("Double value:", floatValue);

Explanation: JavaScript has a single Number type, which is double-precision. I've used the toFixed method to show the difference in precision when limiting the decimal places. In general, most good JavaScript courses should cover these basic skills.

I hope you can see how these examples highlight the difference in precision between float and double types in various languages.

And while the float can be sufficient for many applications, a double offers greater precision, which is crucial in calculations where small inaccuracies can accumulate or lead to significant errors.

As I keep saying, the choice between them often depends on the specific needs of your application and the constraints you're working under, such as memory usage and processing speed.

Performance Considerations: Float vs Double

When I need to make a choice between a float or double, I like to understand their performance implications.

For me, this choice can affect not only the accuracy of my calculations but also the efficiency and resource usage of my program.

So, let's take a deeper dive into some key considerations.

Processing Speed

General Rule: Traditionally, floats were considered faster due to their smaller size and less complex arithmetic operations. However, this is not a hard and fast rule.

Modern Hardware: The performance difference between float and double is minimal on many modern processors, especially in desktop and server environments. Some modern architectures are even optimized for double-precision calculations, making double as fast or even faster in specific scenarios.

GPU and Specialized Hardware: Floats are often faster and more efficient in graphics programming and on GPUs. This is because GPUs are typically optimized for single-precision arithmetic, which aligns well with the requirements of graphics computations.

Memory Usage

Impact on Memory: A double takes twice as much memory as a float, so when working with applications that deal with large arrays or datasets, using a double can significantly increase your memory footprint.

Cache Usage: More memory usage means less efficient use of the cache, which can slow down your program if large datasets are involved.

Precision vs. Performance Trade-off

Precision Needs: If your application requires high precision, double is the preferable choice. For instance, scientific calculations, where small errors can propagate and magnify, demand the precision that double offers.

Performance Needs: For applications where performance and memory usage are more critical than precision, such as real-time systems or applications running on memory-constrained devices, float might be more appropriate.

Application-Specific Considerations

Embedded Systems: Using float can be more efficient in embedded systems or IoT devices with limited memory and processing power.

Data Transfer and Storage: Using float can reduce bandwidth and storage requirements when dealing with large-scale data transfer over networks or storing massive amounts of data.

Best Practices

Profiling is Key: It's important to profile your application to understand the impact of using float vs double. Optimization without measurement can lead to premature and unnecessary complications.

Consider the Context: Always choose the type based on the specific needs of your application. For example, in a desktop scientific application, the choice might lean towards double for precision, while in a mobile game, a float might suffice for performance.

So, as I'm sure you can see, the decision between float and double should be guided by the specific requirements of your application.

And, when you're not sure which to choose, remember to consider factors like precision, processing speed, memory usage, and the hardware on which the application will run. Balancing these factors will help ensure that your program is both efficient and effective in its calculations.

Applications and Practical Uses of Float and Double

As I've discussed already, knowing where and why to use float and double can significantly impact the effectiveness of your application.

Let's now explore some real-world scenarios and applications where the choice between these two types is particularly important.

Scientific Computing

Double for Precision: In fields like physics, astronomy, and chemistry, the precision of calculations and accurate results are paramount. That's why the double is often the go-to choice here because small errors can accumulate over time, leading to significant inaccuracies.

Example: Simulating molecular dynamics or calculating astronomical distances.

Graphics Processing

Float in Graphics: In graphics programming, especially in real-time rendering like video games or simulations, float is commonly used. This offers a balance of performance and sufficient precision for visual details, making the float a practical choice.

Example: Real-time rendering in games where frame rate and memory usage are more critical than the absolute precision of each pixel's color value.

Financial Applications

Precision Matters: In financial applications, rounding errors can lead to significant issues, so these tend to use the double. However, for monetary values, fixed-point types or specialized decimal types are often better choices to avoid floating-point arithmetic issues.

Example: Calculating interest rates, mortgage amortizations, or complex financial models.

Engineering Applications

Depends on the Requirement: Engineering applications, such as CAD software or structural analysis programs, might use the double for higher precision in measurements. However, less critical calculations or preliminary designs might use float.

Example: Precision engineering designs where minute differences can be crucial.

Mobile and Web Applications

Float for Efficiency: In mobile and web applications, where performance and memory usage are critical (especially on lower-end devices), the float can be more efficient.

Example: Mobile apps that perform basic calculations or simple data visualizations.

Data Analysis and Machine Learning

Mixed Usage: The choice in data science and machine learning tends to vary. Training models might use double for precision, but once trained, the models might use float to improve performance during inference, especially on specialized hardware like GPUs.

Example: Training a neural network on a powerful server using double, then deploying it on a mobile device using float.

Embedded Systems

Float for Resource Constraints: In embedded systems or IoT devices with stringent memory and processing constraints, float is often preferred.

Example: Sensor data processing in a small IoT device.

Network and Data Transfer

Float to Save Bandwidth: When transferring large amounts of data over networks, using float can reduce data size, thus saving bandwidth and reducing transmission time.

Example: Sending sensor data from a network of IoT devices to a central server.

So, as you can tell in each of these scenarios, the choice between float and double hinges on balancing precision with performance, memory usage, and the specific demands of the application.

As a developer, understanding these needs is essential for making the right choice and also for ensuring your application performs optimally in its intended environment.

Pitfalls & Common Mistakes With Float And Double

When working with float and double types, there are several pitfalls and common mistakes that programmers need to be aware of.

Being mindful of these can save you from subtle bugs and inaccuracies in your programs.

Let's explore some of these issues and best practices to avoid them.

1. Loss of Precision

Issue: Both float and double cannot precisely represent all decimal fractions, leading to rounding errors.

Example: Accumulating errors in a loop or when dealing with very large or very small numbers.

Best Practice: Be cautious with equality checks and repetitive arithmetic operations. Consider using BigDecimal or similar types in languages like Java for precise decimal arithmetic.

2. Comparing for Equality

Issue: Directly comparing two floating-point numbers for equality is often problematic due to precision errors.

Example: if (floatValue1 == floatValue2) might not work as expected.

Best Practice: Use a threshold for comparison, e.g., if (abs(floatValue1 - floatValue2) < threshold).

3. Overflow and Underflow

Overflow: Occurs when a number exceeds the maximum value the type can represent.

Underflow: This happens when a number is closer to zero than the smallest representable value.

Best Practice: Implement checks for these conditions, especially in loops or iterative calculations.

4. Choosing the Wrong Type for the Context

Issue: Using float when double is needed for precision, or vice versa, can lead to inefficiencies or inaccuracies.

Best Practice: Assess the requirements of your application carefully, considering both precision needs and performance constraints.

5. Misunderstanding Language-Specific Behavior

Issue: Different programming languages might handle floating-point numbers slightly differently, especially regarding default types and precision.

Best Practice: Understand how your chosen language handles floating-point arithmetic and what defaults it uses.

6. Ignoring Environmental Factors

Issue: The behavior of floating-point calculations can vary based on hardware and compiler optimizations.

Best Practice: Test your application in real-world conditions and across different environments to ensure consistent behavior.

7. Not Considering Alternative Types

Issue: In some cases, other types might be more suitable than float or double, such as fixed-point types for financial calculations.

Best Practice: Explore and consider alternative data types that suit your needs better.

8. Inefficient Use in Large Data Sets

Issue: Using double unnecessarily in large data sets can lead to inefficient memory usage and reduced performance.

Best Practice: For large data sets where high precision is not critical, consider using float to optimize memory usage.

By being aware of these potential issues and adhering to best practices, you can ensure that your use of float and double types in your applications is effective and efficient, avoiding common traps and mistakes.

Advanced Topics: Delving Deeper into Float and Double

For those of you who want to deepen your understanding of floating-point numbers, let's also explore some advanced concepts related to floats and doubles.

Floating-Point Arithmetic Rules (IEEE Standards)

IEEE 754 Standard: This is the most widely used standard for floating-point arithmetic in computers. It defines the format for representing floating-point numbers and the rules for arithmetic operations.

Special Values: This standard also defines special values such as NaN (Not a Number), positive and negative infinity, and denormalized numbers.

Rounding Modes: This standard also defines different rounding modes (like round-to-nearest, round-toward-zero), which are crucial for precision-critical applications.

Extended Precision Formats

Long Double: In languages like C and C++, long double represents an extended precision floating-point type. Its size and precision are implementation-dependent and can vary between compilers and architectures.

Quadruple Precision and Beyond: Some systems and languages support quadruple precision (128-bit) and even higher precision formats. These are used in extremely precision-sensitive applications like high-precision scientific computations.

Specialized Floating-Point Libraries

Arbitrary Precision Libraries: For applications requiring precision beyond that offered by a double, libraries like GMP (GNU Multiple Precision Arithmetic Library) or MPFR (Multiple Precision Floating-Point Reliable Library) can be used. These allow calculations with arbitrary precision, limited only by the system's memory.

GPU-Accelerated Computing: Understanding how GPUs handle floating-point calculations, especially considering their optimization for single-precision (float) arithmetic, can be crucial in fields like deep learning and large-scale simulations.

Impact of Compiler Optimizations

Compiler Flags: Different compiler optimizations can significantly affect floating-point calculations, sometimes leading to different results on different systems or with different optimization levels.

Consistency vs. Performance: Balancing the need for consistent, predictable results with the desire for performance optimization is a key challenge in floating-point arithmetic.

Floating-Point in Parallel and Distributed Computing

Consistency Across Systems: In parallel and distributed computing, ensuring that floating-point calculations yield consistent results across different systems and architectures is a challenge.

Strategies for Reproducibility: Techniques like using fixed-seed values in simulations or enforcing IEEE compliance across systems can help maintain consistency.

I've only scratched the surface of these advanced topics, but I'd highly encourage you to dive even deeper if you'd like to gain a more comprehensive understanding of floating-point numbers and their handling in modern computing.

For me, this type of knowledge is not just academic, as it has practical applications in numerous fields, from scientific research to financial modeling, and can be the key to solving complex problems in innovative and efficient ways.

Wrapping Up: Float vs Double

So there you have it! We've now covered everything you need to know about float vs double.

Whether you're at the start of your programming journey or a pro who's looking for a refresher, we've covered floating-point numbers, the difference between float and double, and how to use float and double in different programming languages.

I've also included tips on choosing between float and double for real-world applications, along with advice on common pitfalls to watch out for with float and double. We even delved into some advanced concepts for floating-point numbers if you want to really stretch yourself.

I hope you've enjoyed learning more about float vs double, and feel free to leave a comment below!

As always, happy coding!

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By Robert Johns

Technical Editor for | 15+ Years in Python, Java, SQL, C++, C#, JavaScript, Ruby, PHP, .NET, MATLAB, HTML & CSS, and more... 10+ Years in Networking, Cloud, APIs, Linux | 5+ Years in Data Science | 2x PhDs in Structural & Blast Engineering

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