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Floating-point types

Learn double and floating-point numbers.

The double type

Decimal numbers in Dart are stored in the double type. A double is a 64-bit IEEE 754 floating-point number.

Example: double price = 19.99;. Decimals suit real values like money, temperature, measurements.

In Dart the division operator / always returns a double. So 5 / 2 gives 2.5, not 2. For integer division you use ~/ (we will see it later).

Scientific notation

You can write very large or very small decimals using scientific notation. For example 1e3 is 1000.0; 3.14E-2 is 0.0314.

The letter e or E means 'times 10 to the power of'. The number after it is the exponent. This form is common in physics and engineering.

The result is still a double. So var x = 1e3; makes x a double, not an int.

Practice double variable

Declare double price = 19.99; and print it with print(price);.

Starter code

main.dart
// Declare a double variable

Sample solution

main.dart
void main() {
  double price = 19.99;
  print(price);
}

Expected output

19.99

Questions and answers

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

1 What is the result of 5 / 2 in Dart?

main.dart
5 / 2
  • 2.5 Correct answer
  • 2
  • Throws an error
  • 3

Explanation: / always returns a double.

2 Floating-point type

Question 
____ price = 9.99;
Answer 
double price = 9.99;

Explanation: double is for decimal numbers.

3 Decimal concepts

Term Meaning
double Floating-point
int Integer
1e3 Scientific
/ Division (double)

All lessons in Beginner

1 Dart basics

  1. What is Dart?
  2. Your first program
  3. dart run
  4. Comments
  5. String interpolation
  6. Summary - Dart basics

2 Variables

  1. var and type
  2. final
  3. const
  4. late
  5. Null safety
  6. Summary - Variables

3 Data types

  1. Integer types
  2. Floating-point types
  3. bool and String
  4. Type inference
  5. dynamic
  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. Null-aware operators
  6. Summary - Operators

6 Strings

  1. Creating strings
  2. String interpolation
  3. length and methods
  4. substring
  5. contains and indexOf
  6. Summary - Strings

7 Conditionals

  1. The if statement
  2. else and else if
  3. switch
  4. Pattern matching
  5. Ternary
  6. Summary - Conditionals

8 Loops

  1. The for loop
  2. The while loop
  3. The do-while loop
  4. for-in
  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 Lists

  1. Creating lists
  2. List access
  3. add and remove
  4. length and contains
  5. List methods
  6. Summary - Lists

11 Sets and Maps

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

12 Functions

  1. Defining functions
  2. Return values
  3. Arrow functions
  4. Optional parameters
  5. First-class functions
  6. Summary - Functions

13 Null safety in depth

  1. Nullable types
  2. Null-aware operators
  3. The ! operator
  4. late
  5. Null check
  6. Summary - Null safety

14 Class basics

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

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. split and join
  2. replace
  3. trim and pad
  4. RegExp
  5. StringBuffer
  6. Summary - Advanced strings

17 Enums

  1. Defining enums
  2. Enum values
  3. Enhanced enums
  4. switch with enum
  5. Enum and patterns
  6. Summary - Enums

18 Exceptions

  1. try/catch
  2. throw
  3. finally
  4. The Exception class
  5. on clause
  6. Summary - Exceptions

19 Async basics

  1. Future
  2. async/await
  3. then
  4. Future.error
  5. Future.wait
  6. Summary - Async basics

20 Beginner final

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