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.
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.
Yes. Proportion Solver (Solve for X) is completely free, with no sign-up and no usage limits.
Yes. Proportion Solver (Solve for X) runs in any modern web browser. There is nothing to download or install.
Yes. Proportion Solver (Solve for X) runs entirely on your device in your browser, so nothing you enter is uploaded to a server.