Math Calculators
Ratio Calculator
Simplify any ratio to lowest terms and scale it for recipes, mixes, and models. Enter a:b, get the cleanest form plus a scaled version in one step.
Private by design: this tool runs 100% in your browser. Nothing you enter is sent, stored, or tracked.
How to use this calculator
- Enter both parts of the ratio (a and b).
- See the simplified ratio instantly.
- Optionally enter a scale factor to scale it up or down.
The method
Divide both parts by their greatest common divisor (GCD). Scaling: multiply both simplified parts by the same factor.
Worked example
12:18 simplifies to 2:3 (both divisible by 6). A 2:3 paint mix scaled ×5 becomes 10:15.
About this tool
Simplify any ratio to lowest terms and scale it for recipes, mixes, and models. Enter a:b, get the cleanest form plus a scaled version in one step.
Frequently asked questions
Ratio vs. fraction — what's the difference?
A ratio compares two quantities (2:3 flour to sugar); a fraction is one number (2/5 of the mix is flour). Related, not identical.
How do I scale a recipe up or down?
Simplify first (this tool), then multiply both parts by the same number. Doubling a 2:3 recipe? Use 4:6.
Can it do three-part ratios like 1:2:3?
This version handles two-part ratios, which covers recipes, mixes, and odds. Three-part ratios are on the roadmap.
What is a GCD?
The greatest common divisor — the largest number dividing both parts. 12 and 18 share GCD 6, so 12:18 → 2:3.