Proportion Solver
Fill in three of the four values in a proportion and this solver finds the missing one by cross multiplying. A proportion says two ratios are equal, written a over b equals c over d, and it appears constantly in scaling recipes, converting units, reading maps, mixing solutions, and similar-triangle geometry. Leave any single box empty, and the tool treats it as the unknown x, then cross multiplies and divides to get the exact answer. It works whether the missing value is on the top or the bottom, and it accepts decimals. The result includes a short note showing the cross-multiplication step so you can follow the reasoning, not just copy a number. Everything is computed locally in your browser, so the answer appears instantly and nothing you enter is uploaded.
How to use Proportion Solver (Solve for X)
- Enter the three known values of the proportion.
- Leave the unknown value blank.
- Read the solved value of x with the work shown.
Frequently asked questions
What is a proportion?
A proportion states that two ratios are equal, written a over b equals c over x, and the tool solves for the missing value.
How does cross multiplication solve for x?
It multiplies across the equals sign so a times x equals b times c, then divides to isolate x.
Can the missing value be in any position?
Yes. Leave one of the four slots blank and the tool cross multiplies to find it.
What is Proportion Solver (Solve for X)?
Fill in three of the four values in a proportion and this solver finds the missing one by cross multiplying. A proportion says two ratios are equal, written a over b equals c over d, and it appears constantly in scaling recipes, converting units, reading maps, mixing solutions, and similar-triangle geometry.
Is Proportion Solver (Solve for X) free to use?
Yes. Proportion Solver (Solve for X) is completely free, with no sign-up and no usage limits.
Does Proportion Solver (Solve for X) work in a web browser?
Yes. Proportion Solver (Solve for X) runs in any modern web browser. There is nothing to download or install.
Is my data private with Proportion Solver (Solve for X)?
Yes. Proportion Solver (Solve for X) runs entirely on your device in your browser, so nothing you enter is uploaded to a server.
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