How to use the Ratio Calculator
- Enter A and B to simplify the ratio.
- Enter C or D to solve the proportion A : B = C : D.
- Copy the result.
Proportions
If A : B = C : D, then D = B × C ÷ A. A 16 : 9 screen 1,920 pixels wide is 1,080 pixels tall. To simplify, divide both sides by their greatest common divisor: 1920 : 1080 → 16 : 9. For images and video, try the Aspect Ratio Calculator.
Also searched as: simplify ratio, ratio solver, proportion calculator, scale ratio, a:b = c:d.
Tools that pair well with the Ratio Calculator
- Fraction Calculator — Work with fractions and mixed numbers: add, subtract, multiply or divide two fractions and get the simplified answer with steps, as a mixed number and a decimal.
- Percentage Calculator — Seven everyday percentage calculations on one page.
- Average Calculator — Paste or type numbers to get the mean, median, mode, range, sum and count instantly.
- Unit Converter — Convert between metric, imperial and technical units in ten categories — with a two-way converter and a table of every unit at once.
Frequently asked questions
How do I scale a recipe with ratios?
Keep the ratio between ingredients and change one amount; solve for the others with A : B = C : D.
Can ratios have decimals?
Yes. The calculator converts them to the smallest whole-number ratio when possible.
Is anything I enter saved or sent?
No. The calculation runs in your browser. Your last inputs are remembered on this device only, so the page opens where you left off.
Can I install Ratio Calculator as a web app and use it offline?
Yes. Ratio Calculator is an installable web app (PWA) — installed from your browser, not downloaded from an app store. Click Install app at the top of this page in Chrome or Edge (Windows, macOS, Linux, ChromeOS) or on Android, use Share → Add to Home Screen on iPhone and iPad, or File → Add to Dock in Safari 17+ on a Mac. It then opens in its own window with its own icon, and because it runs entirely in your browser it keeps working offline. Firefox on desktop can’t install web apps. How installing works.