Ratio Calculator

Overview

What is a Ratio Calculator?

A Ratio Calculator simplifies ratios, solves proportions, and scales them. It reduces a ratio like 8:12 to its simplest form (2:3) by dividing by the greatest common divisor, finds the missing value in a proportion (a:b = c:x), and scales a ratio to a total or by a factor. It shows the working and runs in your browser.

Ratios show up in recipes, mixing, maps, finance, and design — and the common tasks are simplifying them, solving 'fill in the blank' proportions, and scaling them up or down. Doing it by hand means hunting for common factors.

This calculator handles all three, shows the steps, and can convert a ratio to a fraction or percentage. It runs entirely in your browser.

Guide

How to use the ratio calculator

Step 1: Choose a mode: simplify, solve a proportion, or scale

Choose a mode: simplify, solve a proportion, or scale.

Step 2: Enter the ratio values (and the total or factor for scaling)

Enter the ratio values (and the total or factor for scaling).

Step 3: Read the result with the working shown

Read the result with the working shown.

Screens

Ratio Calculator in action

Ratio Calculator simplifying a ratio in the browser. — Ratio result

Solving a proportion and scaling a ratio with working. — Solve/scale

Calculating ratios on a phone, no app installed. — Mobile (stacked)

Details

Simplifying, solving, and scaling ratios

A ratio compares quantities, like 2:3 meaning 'two parts to three'. Simplifying reduces a ratio to its smallest whole-number form by dividing both sides by their greatest common divisor (GCD): 8:12 has a GCD of 4, so it simplifies to 2:3 — the calculator finds the GCD and shows the division. Solving a proportion fills in a missing term where two ratios are equal (a:b = c:x); you cross-multiply and divide, so 2:3 = 10:x gives x = (3 × 10) ÷ 2 = 15. Scaling resizes a ratio: to split a total in a given ratio (share $100 in 2:3, which is $40:$60), the calculator adds the parts (2 + 3 = 5), divides the total by that, and multiplies out each share; to scale by a factor, it multiplies both sides. It can also express a ratio as a fraction (2:3 → 2/3) or as percentages of the whole (2:3 → 40% : 60%). All of it is exact integer arithmetic with the working displayed, so you can follow and reuse the method, and it handles decimals and guards against dividing by zero. Everything computes locally in your browser. For fraction arithmetic, see the Fraction Calculator; for percentages, the Percentage Calculator.

Support

Frequently Asked Questions

How do I simplify a ratio?

Divide both sides by their greatest common divisor (GCD). For 8:12, the GCD is 4, so it simplifies to 2:3. The calculator finds the GCD and shows the division, giving the smallest whole-number form of the ratio — the same idea as reducing a fraction.

How do I solve a proportion (a:b = c:x)?

Cross-multiply and divide: x = (b × c) ÷ a. For 2:3 = 10:x, that's x = (3 × 10) ÷ 2 = 15. Enter the three known values in the proportion mode and the calculator finds the missing one and shows the cross-multiplication step.

How do I split a total in a given ratio?

Add the ratio parts to get the total parts, divide the amount by that, then multiply by each part. To split $100 in 2:3: parts = 5, each part = $20, so the shares are $40 and $60. The scale mode does this, which is handy for dividing money, ingredients, or work.

Can a ratio be turned into a fraction or percentage?

Yes. A ratio a:b is the fraction a/b (2:3 → 2/3), and as percentages of the whole each part is its share of the total (2:3 → 2/5 and 3/5, i.e. 40% and 60%). The calculator can convert ratios to both forms so you can use whichever representation you need.

Does it work with decimals?

Yes. The calculator handles decimal values in ratios and proportions, doing the arithmetic exactly. For simplifying, ratios with decimals can be scaled to whole numbers first; for solving and scaling, the math works directly with the decimals you enter.

What is a ratio used for?

Ratios compare quantities and appear everywhere: recipe and mixing proportions, map and model scales, aspect ratios, financial ratios, and splitting amounts fairly. Simplifying, solving, and scaling ratios are the everyday operations, all of which this calculator handles with the working shown so you can verify and learn the method.

Is it free, and do I need to sign up?

Yes, it's completely free with no account, no trial, and no limit on how many times you use it. It runs entirely in your browser, so there's no sign-in wall — just open the page and calculate.

Is my data private?

Yes. Everything is calculated in your browser — the numbers you enter are never sent to a server, and nothing is stored once you close the tab. That keeps any personal figures (salary, loan, health) on your own device.

Does it work on mobile?

Yes. It runs in your phone's browser with nothing to install, so you can calculate on Android or iOS. The layout adapts to small screens, so entering numbers and reading the result is easy on the go.

Does it work offline?

Once the page has loaded, the calculation runs entirely on your device, so it keeps working without a connection. You only need to be online to open the page the first time — which is also why nothing you enter is uploaded.

Can I copy or share the result?

Yes. You can copy the result to your clipboard with one click, and many results can be shared. Because everything is calculated locally, copying is instant with no upload step.

How accurate is it, and is this professional advice?

The math is accurate for the inputs you give, and the formula is shown so you can verify it. But results are estimates for general use, not professional advice — finance calculators use simplified assumptions and ignore fees and rate changes, and health calculators are general estimates, not medical advice. For important decisions, consult a qualified professional.

Still have questions?

If you can't find the answer you're looking for, feel free to contact our support team.

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