Ratio Calculator
Simplify a ratio
Use a colon, slash or space between terms, e.g. 1920:1080. Two or more terms.
Enter a ratio with at least two terms to reduce it.
Solve a proportion
Fill in three boxes of A : B = C : D and leave one empty. The missing value is solved for you.
Leave exactly one box empty to solve for it.
What is Ratio Calculator
This ratio calculator does two jobs. It reduces any ratio to its lowest whole-number terms, so 1920:1080 becomes 16:9, and it solves a proportion of the form A:B = C:D when one of the four values is unknown. It handles two or more terms, accepts decimals, and shows the equivalent decimal value for a two-term ratio.
How to use
- Type a ratio like 1920:1080 into the first box to reduce it.
- Read the simplified ratio and its decimal value below.
- To solve a proportion, fill three of the A:B = C:D boxes.
- Leave the box you want to find empty and read the answer.
When to use it
Cropping a 1920 by 1080 photo and need the aspect ratio? Enter 1920:1080 and you get 16:9. The proportion solver covers the everyday scale-up: if 2 cups of flour need 3 eggs, how many eggs for 5 cups? Enter 2:3 = 5:? and it returns 7.5. Handy for recipes, map scales, mixing paint or fuel, and converting between units that share a fixed rate.
Frequently asked questions
How do you simplify a ratio?
Divide every term by their greatest common divisor. For 1920:1080 the GCD is 120, so both terms divide down to 16:9. This calculator does that step for you, and it scales decimal ratios like 1.5:3 up to whole numbers first before reducing them to 1:2.
How does the proportion solver work?
A proportion A:B = C:D means A divided by B equals C divided by D, so A times D equals B times C. Leave one box empty and the tool rearranges that equation to find the missing value. For 2:3 = 5:? it computes 3 times 5 divided by 2, which is 7.5.
Can I enter more than two terms?
Yes, the simplify box takes any number of terms. Enter 2:4:6 and it reduces to 1:2:3. The decimal value is only shown for a two-term ratio, since a single decimal cannot represent three or more parts.
Can I share this tool with my inputs pre-filled?
Yes. The URL updates automatically as you type. Copy it from the address bar or use the Share button, and anyone who opens the link will see your exact inputs ready to go.
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