Floating-point types

Learn Double and Float types.

Floating-point types

In Kotlin, floating-point numbers come in two types: Double (64 bit, double precision) and Float (32 bit, single precision). Double is the default floating-point type; for example, writing val pi = 3.14 infers Double.

To use Float, you add the f suffix: val g = 9.81f. Double is preferred where precision matters (scientific calculations, money).

val pi: Double = 3.14159   // 64 bit
val g: Float = 9.81f       // 32 bit (f suffix)

Exercise Compute with Double

Write a fun main(). Declare val pi: Double = 3.14 and val r: Double = 2.0. Print the circle area with println(pi * r * r).

Show example solution

fun main() {
    val pi: Double = 3.14
    val r: Double = 2.0
    println(pi * r * r)
}

Precision warning

Floating-point numbers always hold approximate values; some decimals cannot be represented exactly in binary. For example, 0.1 + 0.2 is not exactly 0.3.

For precise calculations like money, BigDecimal is safer. Float is less precise than Double, so it is rarely preferred.

Test yourself

Float suffix
```
val f = 3.14____
```
Show answer
```
val f = 3.14f
```
Which is the default floating-point type?
- Float
- Double
- Int
- Long
Show answer

Double — Double is the default floating-point type.
Floating-point types: match the terms

Double

64 bit
Float

32 bit
Int

32-bit integer
Long

64-bit integer

Next lesson: Boolean and Char

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