Proportion Calculator
Solve proportions by finding the missing value D in the equation A/B = C/D.
The Proportion Calculator solves the classic proportion equation A/B = C/D by computing the unknown fourth value D. Enter the three known values and the tool instantly returns the missing value along with the complete proportion equation for reference.
Proportions are fundamental in mathematics, science, cooking, engineering, and everyday life. When you scale a recipe, you set up a proportion between the original and desired serving sizes. When you calculate distances on a map, you use the map scale as a proportion. Nurses use proportions to determine correct medication dosages based on patient weight. Engineers apply proportions when designing scale models.
The formula used is straightforward cross-multiplication: D = (B times C) / A. The tool validates the inputs and handles the division, so you do not need to worry about arithmetic errors.
All processing is performed entirely in your browser using JavaScript. Your input values are never sent to any server. No account, sign-up, or internet connection (after page load) is required.
Proportions are fundamental in mathematics, science, cooking, engineering, and everyday life. When you scale a recipe, you set up a proportion between the original and desired serving sizes. When you calculate distances on a map, you use the map scale as a proportion. Nurses use proportions to determine correct medication dosages based on patient weight. Engineers apply proportions when designing scale models.
The formula used is straightforward cross-multiplication: D = (B times C) / A. The tool validates the inputs and handles the division, so you do not need to worry about arithmetic errors.
All processing is performed entirely in your browser using JavaScript. Your input values are never sent to any server. No account, sign-up, or internet connection (after page load) is required.
Calculator
Results
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How to Use
- Enter the three known values: A, B, and C.
- The tool computes D using the formula D = (B x C) / A.
- View the result and the full proportion equation.
FAQ
What formula does this use?
The tool solves A/B = C/D by cross-multiplying to get D = (B x C) / A.
What if A is zero?
If A is zero, the proportion is undefined because division by zero is not possible. The tool will not return a result.
Can I solve for a different variable?
This tool specifically solves for D. To solve for a different variable, rearrange your proportion so that the unknown is in the D position.
Is my data safe in the browser?
Yes. All calculations run locally in your browser using JavaScript. No data is sent to any server.
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