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Random Number

Generate random integers or decimal numbers within your chosen range.

Generator Configuration

Select number type and configure range bounds.

Generated Numbers (0 items) —
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Generate random numbers within a specified range.

About this topic

Random Integers Whole numbers uniformly distributed over a range.

Generates whole numbers between a minimum and maximum value. If duplicates are allowed, numbers are drawn with replacement. If not, they are drawn without replacement.

Key formulas & rules

  • •Includes both min and max bounds
  • •Duplicates can be toggled
  • •Maximum quantity depends on range size
  • •Uses Fisher-Yates for unique draws
  • •Results can be saved to history
  • •Decimals are not included

Examples

Input Output Note
1 to 10, 3 items 4, 8, 2 Duplicates allowed
1 to 5, 5 items 1, 2, 3, 4, 5 No dupes
1 to 100, 2 items 67, 5 Standard
10 to 20, 1 item 15 Single draw

Real-world uses

Lottery numbers Sampling Game mechanics
Random Decimals Floating-point numbers uniformly distributed over a range.

Generates decimal numbers between a minimum and maximum. The precision is controlled by the number of decimal places. Duplicates are always allowed.

Key formulas & rules

  • •Min and max are treated as floats
  • •Decimal places range from 0 to 6
  • •Uniform distribution
  • •Duplicates always allowed
  • •Precision affects the pool size
  • •Can generate 0.0 to 1.0

Examples

Input Output Note
0 to 1, 2 places 0.45, 0.89 Standard
1 to 10, 1 place 3.7, 8.2 Single decimal
0 to 100, 0 places 42, 97 Whole numbers
0 to 1, 6 places 0.123456 High precision

Real-world uses

Statistical simulations Probability models Monte Carlo

Modes & formulas

1

Random Integers

• Click Generate to create new random numbers. • Choose a start and end bound (inclusive). • Decide the quantity and whether duplicates are allowed. • The generator produces integers uniformly at random within the range.
Random(min, max) = Math.floor(Math.random() × (max − min + 1)) + min

Duplicate prevention uses a Fisher–Yates shuffle on the integer range, then takes the first N items. This guarantees uniqueness when duplicates are disallowed.

2

Random Decimals

• Set the minimum and maximum bounds as decimal values. • Specify the number of decimal places (0–6). • The generator returns uniformly-distributed decimal numbers.
Random = Math.random() × (max − min) + min

The number of decimal places controls the rounding precision. Every value in the range is equally likely.

How to use it

Select the number type (Integers or Decimals), set your range and quantity, then click Generate. Click Save to History to store the current results.

Frequently asked questions

Are these numbers cryptographically secure?
No. This tool uses Math.random(), which is a pseudo-random generator. For cryptographic use, use crypto.getRandomValues() instead.
Why can't I generate 10 unique integers between 1 and 5?
There are only 5 possible integers in that range, so 10 unique values is impossible.
Are these numbers truly random?
They are pseudo-random, generated by JavaScript’s Math.random() function. They appear random and are suitable for games or simulations, but are not cryptographically secure.
What does "Allow Duplicates" mean?
If checked, the same number can be generated multiple times. If unchecked, all generated numbers will be unique.
Why can’t I generate 20 unique numbers between 1 and 10?
Because there are only 10 possible integers in that range. You cannot pick 20 unique numbers from a pool of 10.
What is the difference between integers and decimals here?
Integers are whole numbers (1, 2, 3). Decimals include fractional parts (1.5, 2.75) and allow you to set the precision.

Related calculators

Prime Number Check if a number is prime and find factors. Factorial Compute factorials for non-negative integers. GCD / HCF Find the Greatest Common Divisor using Euclidean algorithm. LCM Find the Least Common Multiple of numbers. Number Base Convert between Binary, Octal, Decimal, and Hexadecimal.
Read the full Random Number guide — examples & 18 FAQs