Solve for x in Any Proportion Instantly
Enter three known values, let x mark the unknown. Our Proportion Calculator cross-multiplies and solves in one click — no algebra required.
Note: One of the input values should be an alphabet, e.g., x
Frequently Asked Questions
Stuck on a ratio problem? Type in your numbers, place x where the missing value belongs, and get the exact answer with full cross-multiplication steps shown.
A proportion calculator solves equations of the form a/b = c/d when one value is unknown. Enter the three known numbers, mark the missing one as x, hit Calculate, and the tool returns the answer with a full step-by-step solution.
Cross-multiplication turns a/b = c/x into a × x = b × c. From there, isolate x by dividing both sides by a. The calculator performs every step automatically and displays the working so you can follow the logic.
Any real-world ratio problem: scaling a recipe, converting units, reading a map, calculating dosage, resizing an image, or working through school algebra. If three values are known and one is missing, this tool handles it.
Yes. Put x in whichever position matches your problem — top-left, top-right, bottom-left, or bottom-right. The calculator detects the unknown position and rearranges the cross-multiplication formula accordingly.
Every calculation includes the original equation, the cross-product step, the isolation step, and the final answer. You can copy the full solution with one click using the Copy button on the results panel.
The calculator returns the most precise decimal result. For 4/5 = 6/x, it correctly outputs x = 7.5. If you need the answer as a fraction, divide the numerator result by the denominator shown in the working steps.
Completely free, no sign-up needed. Open the tool, enter your values, and calculate. There are no usage limits and no subscription required.
A ratio compares two quantities (3:4). A proportion states that two ratios are equal (3/4 = 6/8). This calculator works specifically with proportions — it finds the missing term that makes both ratios equal.