Random Number Generator - Generate Any Random Number
Generate one or more random numbers between any minimum and maximum. Instant, fair, and completely free. Use presets for dice, lottery, cards, or set your own custom range.
History
How Random Number Generation Works
True Randomness vs Pseudo-Randomness
There are two fundamentally different types of randomness in computing. True random number generators (TRNGs) derive entropy from physical phenomena - thermal noise in electronic circuits, atmospheric radio noise, or radioactive decay. These are genuinely unpredictable and are used in cryptography and security applications. Hardware security modules and services like Random.org use true randomness.
Pseudo-random number generators (PRNGs) use a mathematical algorithm seeded with an initial value to produce sequences of numbers that appear random. Given the same seed, a PRNG always produces the same sequence - it is deterministic. However, with a sufficiently unpredictable seed (like the current timestamp combined with other system state), the output is statistically indistinguishable from true randomness for all practical everyday purposes. For selecting a person rather than a number, the random name picker applies the same principle to a list of names.
What This Generator Uses
This tool uses JavaScript's Math.random(), which in modern browsers is implemented using the xorshift128+ algorithm - a fast, well-distributed PRNG with a period of 2128. The seed is determined by the browser engine at startup from system entropy sources. For everyday use - games, classroom selection, decision making, lottery picks - this is more than sufficient. For password generation or security-critical applications, use crypto.getRandomValues(), which the browser also provides and which accesses the operating system's cryptographically secure PRNG.
Random Number Applications
Random numbers are used across nearly every field of human endeavor - from entertainment to scientific research. Here is an overview of the most common practical applications. In classroom settings, teachers often combine a random number generator with the name picker and tally counter for fully fair, data-tracked participation.
| Application | Typical Range | Method | Purpose |
|---|---|---|---|
| Lottery pick | 1–49 or similar | Uniform integer draw | Games of chance, fun |
| Dice simulation | 1–6 (or other) | Uniform integer | Board games, tabletop RPGs |
| Classroom selection | 1–30 (class size) | Uniform integer | Fair, unbiased selection |
| A/B testing | 0 or 1 | Bernoulli (50/50) | Split traffic between variants |
| Monte Carlo simulation | 0–1 (float) | Uniform float | Scientific modeling, physics |
| Random sampling | 1–N (population) | Uniform integer without replacement | Statistical research |
| Board game events | 1–100 | Uniform integer | Random event tables |
| Password generation | Character set | Cryptographic PRNG | Security (not this tool) |
Common Dice Combinations
Tabletop role-playing games and board games use a standard set of polyhedral dice, each generating a different range of values. Use the generator above with the corresponding range to simulate any die roll electronically. For group-based games that also need turn-order management, the group generator can split any list of participants into random teams.
| Dice | Notation | Range | Combinations | Average |
|---|---|---|---|---|
| 4-sided die | d4 | 1–4 | 4 | 2.5 |
| Standard die | d6 | 1–6 | 6 | 3.5 |
| Two standard dice | 2d6 | 2–12 | 36 | 7 |
| 8-sided die | d8 | 1–8 | 8 | 4.5 |
| 10-sided die | d10 | 0–9 | 10 | 4.5 |
| 12-sided die | d12 | 1–12 | 12 | 6.5 |
| 20-sided die | d20 | 1–20 | 20 | 10.5 |
| Percentile dice | d100 | 1–100 | 100 | 50.5 |
Probability and Uniform Distribution
On a fair six-sided die, each face has exactly a 1-in-6 chance of appearing - approximately 16.7%. A uniform random number generator maintains this equal probability across the entire range. The chart below shows the theoretical probability for each face of a d6. If you're using dice rolls to time game rounds, the bomb timer adds a fun countdown element to board game sessions.
Theoretical probability per face on a fair d6. In practice, short sequences appear uneven - this is normal. Roll many times and the distribution converges toward equal.
Frequently Asked Questions
Is this generator truly random?
This generator uses JavaScript's Math.random(), which produces pseudo-random numbers using a deterministic algorithm (xorshift128+) seeded with system entropy. For games, classroom selection, decision making, and lottery simulations, it is statistically indistinguishable from true randomness. For cryptographic or security purposes, use a dedicated tool that uses crypto.getRandomValues(). For picking names rather than numbers, the random name picker is purpose-built for that use case.
Can I get reproducible results with a fixed seed?
Not with this tool. The seed is chosen automatically by the browser engine and cannot be set manually. If you need reproducible sequences - for example, to recreate a specific test case - you would need a seeded PRNG implemented in custom JavaScript where you control the initial seed value.
Can the minimum be zero?
Yes. Set the minimum to 0 and the maximum to any positive number. The generator will produce integers from 0 through your maximum (inclusive). This is useful for simulating zero-indexed arrays, percentile rolls, or any scenario where zero is a valid outcome.
Can I generate multiple numbers at once?
Yes. Set "How many?" to any number from 1 to 1,000. Toggle "No repeats" to ensure each result is unique - like drawing lottery balls without replacement. If you request more unique numbers than the range allows, you'll see an error message.
Is this tool suitable for security or cryptography?
No. Math.random() is not cryptographically secure. Do not use this generator to create passwords, encryption keys, security tokens, or any values where predictability would be a security vulnerability. For those purposes, use a password manager or a dedicated cryptographic tool that uses the browser's crypto.getRandomValues() API.