Ratio Calculator
Simplify a ratio, scale it up, or solve for a missing value.
Processing: This tool runs entirely in your browser. Your input and any file you open stay on your device — nothing is uploaded to a server.
How to use the ratio calculator
- Fill in the fields — they start with a worked example.
- Read the answer, and the arithmetic shown beneath it.
- Copy the results, or adjust the inputs to compare scenarios.
About this tool
A ratio compares quantities without fixing their size, so 2:3 and 200:300 describe the same mixture. Simplifying divides both parts by their greatest common divisor.
Solving for a missing value uses cross-multiplication: if A is to B as C is to D, then A×D equals B×C — the arithmetic behind scaling a recipe or a drawing.
Common uses
- Scaling a recipe or a mix to a different quantity.
- Reducing an aspect ratio to its simplest form.
- Splitting an amount in a given ratio.
Frequently asked questions
- How do I split an amount in a ratio?
- Add the parts to get the total number of shares, divide the amount by that, then multiply by each part. The split is shown when you enter a total.
- What does 3:4 mean as a fraction?
- Three parts out of seven, so 3/7 of the whole — not 3/4. That confusion is the most common ratio mistake.
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