Generate a random floating point number in given range

Scale Math.random into [min, max).

JavaScriptNode.js & browsers Version 1.0.0 · MIT · .md

function randomFloat(min, max) { return Math.random() * (max - min) + min; }

Usage

const x = randomFloat(1.5, 2.5);
x >= 1.5 && x < 2.5; // → true
randomFloat(1.5, 2.5); // e.g. 2.0381

Lines marked → were executed in Node.js 22 and in headless Chromium, and each result was compared with the value shown. Lines marked e.g. are illustrative.

Know the limits

• Results fall in [min, max). Floating-point rounding can occasionally produce max itself; clamp if that matters.

The function above is the code the usage lines run. It does not validate its arguments; add checks where it receives untrusted input.

Keep exploring

• Generate a random boolean — Return true or false with equal probability.
• Generate a random hex color — Return a #rrggbb color from 24 random bits.
• Generate a random integer in given range — Return an integer from min to max, both included.