Random Number Generator
Generate random integers or decimals within a range. This page includes a simple integer generator and a comprehensive version that can produce multiple numbers at once.
Random Integer Generator
Creates a random integer between a lower and upper limit (inclusive). Both limits must be whole numbers.
Comprehensive Version
Generate one or many random integers or decimals. Set decimal precision when using decimal mode (up to 15 decimal places).
Quick note
Browser-based generators use pseudo-random algorithms. Results are suitable for games, sampling, and everyday use — not cryptographic security.
What is a random number?
A random number is a value selected from a set of possible numbers where each value has an equal chance of being chosen (for uniform generators). There is no predictable pattern between successive draws. For example, if you randomly pick the height of a student from a school, the distribution might follow a normal curve — but each individual pick is still random within that population.
In practice, “random” often means uniformly distributed over an interval: every integer from 1 to 100 is equally likely when using our integer generator.
What is a random number generator?
A random number generator (RNG) is a device or algorithm that produces numbers within a defined scope. Physical examples include dice, coin flips, and lottery ball machines. Digital tools like this page use software to approximate randomness.
Common uses include:
- Games & contests: Picking winners, shuffling teams, or rolling virtual dice.
- Statistics & simulations: Monte Carlo methods, bootstrapping, and sample selection.
- Education: Probability exercises and classroom demonstrations.
- Testing: Generating test data with varied inputs.
Pseudo-random vs true random
Most computer random number generators are pseudo-random. They use a deterministic algorithm seeded from an initial value, producing a sequence that appears random but eventually repeats. For everyday tasks — picking a number, simulating dice, or generating sample data — pseudo-random output is more than adequate.
True random numbers come from physical processes such as radioactive decay or atmospheric noise. They are required for cryptography and high-security applications. This calculator is not designed for cryptographic use.
How to use this random number generator
- Simple integer mode: Enter lower and upper limits (whole numbers), then click Generate. The result is a random integer between those limits, inclusive.
- Comprehensive mode: Set a decimal or integer range, choose how many numbers to generate (1–500), pick Integer or Decimal, and set decimal precision if needed.
- Copy results: Use the Copy button to copy the latest generated value to your clipboard.
Example: Lower = 1, Upper = 6 simulates a fair six-sided die. Lower = 0.2, Upper = 112.5 with Decimal mode might produce values like 47.381926.
Integer vs decimal random numbers
Integer mode rounds limits to whole numbers and returns values like 42 or −7. Decimal mode allows fractional bounds and returns values rounded to your chosen precision. If lower limit exceeds upper limit, the calculator automatically treats the smaller value as the minimum.
Real-world applications
- Lotteries & raffles: Assign each entry a number, then generate a winning number in range.
- Experiments: Randomly assign subjects to control and treatment groups.
- Quality control: Select random items from a batch for inspection.
- Programming practice: Test functions with varied numeric inputs — pair with our scientific calculator for expression checks.