How to use this calculator
- Enter your own values in the labeled fields. Check the units and assumptions before comparing results. Only the fields needed for your selected calculation mode are shown.
- Your answer updates automatically. Review the calculation steps to see exactly how it was calculated.
- Copy, share, save, or download your result. Saved inputs stay on this device.
How the calculation works
A ratio expresses a comparison using a shared scale. Whole-number simplification divides both terms by the greatest common divisor. Proportion mode instead uses cross multiplication to solve a/b = c/x. Match the meaning and units of each pair before applying the relationship.
A worked example
12:18 simplifies by dividing both terms by 6, giving 2:3. For 2/3 = 8/x, x = 12.
Reading your result
Use the main result together with its units and supporting figures. Display values are rounded; calculations keep their underlying precision. A change in inputs or assumptions can change the answer. Compare the step-by-step working with your intended use before relying on an estimate.
Frequently asked questions
Can I simplify decimal ratios?
This version requires positive whole numbers in simplification mode.
Are zero denominators accepted?
No. The first numerator and denominator must be positive.
Sources & methodology
This calculator uses the mathematical identity and assumptions stated above. No current rates, prices, or external data are loaded. Conversion tools use international unit definitions.
Formula review: October 24, 2026. Read our methodology.