Ratio Calculator

How Ratio Calculator works

Simplify a ratio to its lowest terms and solve for the missing side at any scale. Everything happens inside this page: the tool reads your input, runs the calculation or conversion locally, and hands the result back to you. Nothing is transmitted, because there is no backend to transmit it to.

That design choice is deliberate. Most free tool sites upload your files to a server, process them there, and quietly keep a copy. Toolcin cannot do that — the site is a set of static files. If your connection dropped the moment the page finished loading, every tool would still work.

Simplify, then scale

Enter a ratio as two numbers and the tool divides both by their greatest common divisor. 16:9 is already in lowest terms; 1920:1080 reduces to 16:9 by dividing both by 120, which is the whole point — the screen resolution and the aspect ratio are the same relationship.

The second pair scales the ratio: give it a known first value and it returns the matching second value. If A:B is 16:9 and A is 1280, B is 720.

Ratios that keep catching people out

A ratio is not a fraction of a total. Mixing paint 3:1 means three parts to one part, so the total is four parts — a quarter of the mixture is the second component, not a third. Asking “what is 3:1 as a percentage” requires deciding which side you mean.

Aspect ratios are the same trap. A 21:9 screen is not 21/9 times taller than it is wide; it is 21 units wide for every 9 units tall, which is 2.33:1.

Where this gets used

Screen and image dimensions, recipe scaling, map scales, gear ratios and concrete mixes. In every case the useful step is the same: reduce to the smallest whole numbers so two different-looking pairs can be compared.

Good to know

• Works offline once loaded, including on flights and in locked-down networks.
• No file size limit beyond your device's own memory.
• Free to use, with no account and no usage counter.
• Results are produced locally, so they are not logged or shared with anyone.

Questions