Random Number Calculator
Generate a single random number between any two values, with optional decimal places. Fast, simple, and runs entirely in your browser.
Reviewed October 7, 2026 Runs in your browser — inputs are never stored
This tool performs standard mathematical operations for educational and reference purposes. Always double-check results for critical academic or professional work.
About the Random Number Calculator
A random number calculator is a lightweight tool that produces a single random value between any two numbers you choose, with full control over decimal places. It is ideal for quick decisions where a single unbiased outcome is needed — breaking a tie, picking a winner, simulating a coin flip, generating a test percentage, or choosing a random temperature for an experiment. Unlike the multi-value generator, this tool focuses on one result at a time and supports decimals from zero to ten places, so it works equally well for whole-number draws and fine-grained scientific values. The calculator uses the browser's uniform pseudo-random engine, which is appropriate for everyday use, teaching probability, and generating demo data, but not for cryptographic applications. By delivering an instant, private result with no sign-up or installation, it removes human bias from small decisions and makes simple randomisation effortless. Whether you need a fair coin flip or a random decimal for a simulation, the tool gives you a trustworthy answer in one click.
How to use it
- 1Enter the lower and upper bounds of the range.
- 2Set decimal places if you need fractional results.
- 3Generate a single random value.
- 4Copy the result if you need to paste it elsewhere.
- 5Generate again for an independent draw.
Worked example
range 0 to 1 with 4 decimal places might yield 0.7381 — useful for simulations. Range 1–10 with 0 decimals behaves like a ten-sided die. Each press is independent unless you intentionally seed elsewhere.
How it works
How it works
The calculator uses Math.random() × (max − min) + min to produce a uniformly distributed value in your range, then rounds it to your chosen number of decimal places.
Practical examples
- Coin flip: min 0, max 1, decimals 0 → 0 or 1.
- Random percentage: min 0, max 100, decimals 1 → e.g. 42.7.
- Random decimal: min 0, max 1, decimals 4 → e.g. 0.6173.
- Random temperature: min −10, max 40, decimals 0 → integer °C.
Common use cases
- Quick decisions and tie-breakers.
- Generating test values and demo data.
- Teaching probability and uniform distributions.
- Simulating simple random events.
Frequently asked questions
A:Yes. Set "Decimal places" to any value from 0 to 10. The result is rounded to that many decimals.
A:The result is in the half-open interval [min, max) — it can equal min but will almost never equal max exactly. For integer ranges use the Random Number Generator instead.
A:This tool produces a single value (which can be decimal), while the Generator produces multiple integers at once with unique and sort options.
Reviewed for accuracy · Last updated October 7, 2026
Calculations use standard, well-established mathematical identities and algorithms with no approximation beyond normal floating-point precision.
CalcWisee Editorial Team
Calculator development and formula review
CalcWisee is an independent site founded by Ayman. Every calculator is built from a published formula or official definition, tested against hand-worked examples before it goes live, and corrected promptly when a reader reports an issue to ayman@calcwisee.com.
Expertise: Financial mathematics, Health and fitness formulas, Applied mathematics, Unit conversion standards
References & sources
Related guides
Random Number Generator: How It Works and When to Use One
Learn how a random number generator works, the math behind uniform randomness, and practical uses — with a free tool to generate random numbers in any range.
How to Calculate Percentages: 4 Everyday Problems
A plain-English guide to the four percentage problems you actually use — tips, discounts, growth, and reverse percentages — with worked examples.
Percentage Calculator: Solve Percentage Problems Easily
Master everyday percentage math — find a percent of a number, reverse percentages, percentage increase and decrease, discounts, tax, and tips — with clear formulas and a free calculator.