Ratio Calculator
Simplify a ratio such as 1920 : 1080 to its lowest terms, or scale a ratio to find a missing value. Enter A : B, then the value you know to solve A : B = C : D.
Example: a 16 : 9 screen that is 1920 pixels wide is 1080 pixels tall. Enter A = 16, B = 9 and C = 1920 to find D.
How to Use the Ratio Calculator
- Enter the two parts of your ratio in A and B, for example 16 and 9.
- Read the simplified ratio and the 1 : n and n : 1 forms in the result panel.
- To scale the ratio, choose whether you know C or D, then enter that value.
- Read the missing value in the result, then copy it or click Reset to start again.
Example
Find the height of a 16 : 9 image that is 1920 px wide
- Input
- A = 16, B = 9, C = 1920
- Output
- 16 : 9 = 1920 : 1080 D = 1080 Simplified: 16 : 9 As 1 : n → 1 : 0.5625 As n : 1 → 1.777778 : 1
About the Ratio Calculator
A ratio compares two amounts. Ratios are used for screen and image aspect ratios, recipe and mixing quantities, map and model scales, and splitting costs or resources. Scaling a ratio keeps the same proportion while changing the size.
To simplify, the calculator divides both parts by their greatest common divisor, so 1920 : 1080 becomes 16 : 9. Decimal ratios are scaled to whole numbers first, so 1.5 : 2 becomes 3 : 4. To scale, it solves A : B = C : D: if you know C, then D = C × B ÷ A, and if you know D, then C = D × A ÷ B.
A and B must be greater than 0, and the value you scale by must be 0 or more. Results are rounded to at most 6 decimal places. The calculation runs in your browser with JavaScript, and this tool does not send what you enter to a Usevanta server.
Frequently Asked Questions
How do I simplify a ratio?
Divide both parts by their greatest common divisor. For 150 : 250 the greatest common divisor is 50, so the ratio simplifies to 3 : 5. Enter A and B and the calculator does this for you.
How do I find a missing value in a ratio?
Enter the ratio in A and B, choose which value of the second pair you know, and type it in. For 2 : 3 with C = 500, the calculator returns D = 750.
Can I use decimals?
Yes. Decimal ratios are scaled to whole numbers before simplifying, so 0.5 : 1.5 becomes 1 : 3.
Why can’t A or B be zero?
A ratio with a zero part cannot be scaled, because solving for the missing value would mean dividing by zero.
Can I use it for aspect ratios?
Yes. Enter the aspect ratio, for example 16 : 9 or 4 : 3, then the known width or height to get the other dimension.
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