Random Number Generator
Generate random numbers within a specified range.
Understanding Random Number Generator
A random number generator produces a numerical value selected from a specified range. This calculator generates a random integer between the minimum and maximum values you provide, with both endpoints included in the possible results.
For example, if the minimum is 1 and the maximum is 100, any integer from 1 through 100 can be generated. Because there are 100 possible values, each individual value has a theoretical probability of 1%, assuming uniform random selection.
Using the result in context
Random Number Generator is built for a specific practical task, so the quality of the output depends on using the options for the purpose you have in mind. The page's available controls and inputs determine how the result is produced; when present, they include Minimum Value, Maximum Value.
When the result is an estimate
Use the output as a practical aid and review the settings before acting on it. If the tool offers multiple choices, selecting a different option can intentionally produce a different result, so the selected method should match the task rather than simply using the default.
Random Number Generator
A random number generator produces a numerical value selected from a specified range. This calculator generates a random integer between the minimum and maximum values you provide, with both endpoints included in the possible results.
For example, if the minimum is 1 and the maximum is 100, any integer from 1 through 100 can be generated. Because there are 100 possible values, each individual value has a theoretical probability of 1%, assuming uniform random selection.
Inclusive Random Range
This calculator uses an inclusive range, which means that both the minimum and maximum values are valid results. The number of possible integer values is calculated by subtracting the minimum from the maximum and adding one.
For a range from 10 to 20, there are 11 possible values: 10, 11, 12, and so on through 20.
How the Random Number Is Calculated
JavaScript's built-in Math.random() function produces a pseudorandom decimal value greater than or equal to 0 and less than 1. The calculator transforms this value into an integer within the selected range.
The multiplication determines the size of the available range, while the floor operation converts the resulting value into an integer. Adding the minimum shifts the result so that it starts at the requested lower boundary.
Uniform Random Selection
The calculator is designed to select each integer in the specified range with the same theoretical probability. If there are N possible values, the probability of selecting any particular value in one generation is:
Percentage = (1 / N) × 100
This does not mean every number will appear equally often during a small number of generations. Random variation is expected. Over a sufficiently large number of independent generations, the observed frequencies tend to become closer to the expected distribution.
Pseudorandom Numbers
Computers commonly generate pseudorandom numbers using algorithms rather than obtaining randomness directly from a physical process. JavaScript's Math.random() is intended for general purpose randomized behavior such as games, simulations, testing, exercises, and simple random selections.
The generated values should not be treated as cryptographically secure random numbers. Applications requiring security-sensitive randomness, such as generating passwords, authentication tokens, or encryption keys, should use an appropriate cryptographic random source instead.
Common Uses
Random number generation is useful for simulations, probability exercises, games, randomized testing, choosing a number from a range, creating sample selections, and other situations where an unpredictable numerical value is useful.
How to Use the Calculator
Enter the smallest integer you want to allow in the Minimum Value field and the largest integer in the Maximum Value field. Then calculate to generate one random integer from the inclusive range.
The result also shows the number of possible values, the theoretical probability of each value, the selected range, and the calculation used to produce the generated number.
Minimum = 1
Maximum = 100
Possible Values = 100
Each Value Probability = 1%
Generated Number = Random integer from 1 to 100
Disclaimer
This calculator is intended for informational purposes only. While we strive for accuracy, we cannot guarantee that every result is correct for every situation.