Ratio Calculator
Simplify ratios, find the missing number in a proportion, share a total in a ratio and resize images or screens without distortion, all in one place.
- Simplify & solve
- Split in a ratio
- Aspect ratios
- Step-by-step
Simplify a ratio
Fill in the boxes. The answer appears as you type.
Solve a proportion A : B = C : ?
Fill in the boxes. The answer appears as you type.
Split a total in a ratio
Fill in the boxes. The answer appears as you type.
Resize keeping the aspect ratio
Fill in the boxes. The answer appears as you type.
What is a ratio calculator?
A ratio compares quantities, such as 2 parts water to 3 parts flour (2:3). A ratio calculator does the common ratio jobs for you: reducing a ratio to its simplest form, solving proportions where one value is missing (3:4 = 15:?), splitting an amount according to a ratio (sharing $600 in the ratio 2:3) and keeping an image’s aspect ratio when you change its width. Every answer shows the working and a spreadsheet formula.
How to use Ratio Calculator
- Pick the card that matches your question.
- Type the numbers; decimals like 1.5:2.25 work too.
- Read the answer and the sentence below it.
- Open “Show working” for the steps and a formula you can paste into Excel or Google Sheets.
Ratio formulas
- Simplify: divide every part by their greatest common divisor. 24:36 → ÷12 → 2:3.
- Proportion: A:B = C:D means A × D = B × C, so D = B × C ÷ A.
- Split a total: one part = total ÷ sum of the parts; multiply by each part.
- Aspect ratio: new height = new width × original height ÷ original width.
Why use this ratio calculator
- Answers as you typeNo Calculate button. Change any number and every result updates instantly.
- Shows the workingEach answer has a plain-English sentence, the steps and a formula for Excel or Google Sheets.
- Three-part ratiosSimplify or split ratios like 2:3:5, not just two parts.
- PrivateYour numbers are calculated on your device and never sent anywhere.
Common uses
- Cooking and mixing. Scale recipes, concrete mixes and paint ratios.
- Sharing money. Split rent, profits or bills fairly.
- Images and screens. Find heights for 16:9 or 4:3 at any width.
- Homework. Check ratio and proportion problems with steps.
More calculators: percentage, discount, hours and time card calculators. Browse all everyday calculators.
Example: sharing $600 in the ratio 2:3
Total 600, ratio 2:3 → parts add to 5 → one part is 120 → shares are 240 and 360.
What to expect from the result
Ratios use positive numbers. Decimals are simplified by scaling to whole numbers first, up to six decimal places.
Ratio Calculator questions
How do I simplify a ratio?
Divide every part by the largest number that divides them all (the greatest common divisor). 24:36 has a GCD of 12, so it simplifies to 2:3.
How do I solve a proportion?
Cross-multiply. For 3:4 = 15:x, x = 4 × 15 ÷ 3 = 20. Use the “Solve a proportion” card.
How do I divide an amount in a ratio?
Add the ratio parts, divide the amount by that sum, then multiply by each part. $600 in 2:3 gives $240 and $360.
What is 16:9 at 1280 pixels wide?
1280 × 9 ÷ 16 = 720, so 1280 × 720.
Can I simplify a ratio with decimals?
Yes. 1.5:2.25 is scaled to 150:225 and simplified to 2:3.