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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)

Practice 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).

Sample solution

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

Expected output

12.56

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.

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 Float suffix

Question 
val f = 3.14____
Answer 
val f = 3.14f

Explanation: Float literals are written with the f suffix.

2 Which is the default floating-point type?

  • Float
  • Double Correct answer
  • Int
  • Long

Explanation: Double is the default floating-point type.

3 Floating-point types: match the terms

Term Meaning
Double 64 bit
Float 32 bit
Int 32-bit integer
Long 64-bit integer

All lessons in Beginner

1 Kotlin basics

  1. What is Kotlin?
  2. Your first program
  3. The main function
  4. Comments
  5. String templates
  6. Summary - Kotlin basics

2 Variables

  1. val and var
  2. Type inference
  3. const
  4. lateinit
  5. by lazy
  6. Summary - Variables

3 Data types

  1. Integer types
  2. Floating-point types
  3. Boolean and Char
  4. String
  5. Any and Unit
  6. Summary - Data types

4 Project: Calculator

  1. Project design
  2. Add and subtract
  3. Multiply and divide
  4. Error handling
  5. Putting it together

5 Operators

  1. Arithmetic operators
  2. Assignment operators
  3. Comparison operators
  4. Logical operators
  5. Elvis operator
  6. Summary - Operators

6 Strings

  1. Creating strings
  2. String templates
  3. String methods
  4. substring
  5. split and replace
  6. Summary - Strings

7 Conditionals

  1. The if statement
  2. else and else if
  3. if expression
  4. when
  5. when expression
  6. Summary - Conditionals

8 Loops

  1. The for loop
  2. The while loop
  3. The do-while loop
  4. Range
  5. break and continue
  6. Summary - Loops

9 Project: Shopping cart

  1. Cart design
  2. Adding items
  3. Calculating totals
  4. Listing the cart
  5. Putting it together

10 Arrays

  1. Creating arrays
  2. Array access
  3. Array size
  4. Array loop
  5. Array methods
  6. Summary - Arrays

11 Lists

  1. Creating lists
  2. List operations
  3. List access
  4. List iteration
  5. List methods
  6. Summary - Lists

12 Maps and Sets

  1. Creating sets
  2. Set operations
  3. Creating maps
  4. Map operations
  5. Map iteration
  6. Summary - Maps and Sets

13 Functions

  1. Defining functions
  2. Return values
  3. Expression body
  4. Default parameters
  5. Named arguments
  6. Summary - Functions

14 Null safety

  1. Nullable types
  2. ?, !! and ?:
  3. let
  4. Null check
  5. lateinit
  6. Summary - Null safety

15 Project: To-do CLI

  1. Task model
  2. Adding tasks
  3. Listing tasks
  4. Completing tasks
  5. Putting it together

16 Advanced string operations

  1. Regex
  2. matches and find
  3. replace
  4. StringBuilder
  5. trim and pad
  6. Summary - Advanced strings

17 Enums

  1. enum class
  2. Enum values
  3. Enum properties
  4. when with enum
  5. Enum and range
  6. Summary - Enums

18 Exceptions

  1. try/catch
  2. throw
  3. finally
  4. try expression
  5. Custom exceptions
  6. Summary - Exceptions

19 Class basics

  1. class
  2. Constructor
  3. Properties
  4. Methods
  5. this
  6. Summary - Class basics

20 Beginner final

  1. Project design
  2. Classes
  3. Collections
  4. Error handling
  5. Putting it together