ToolsPopper's Proportion Calculator solves the classic rule-of-three problem: given that A is to B as C is to X, it finds the unknown X. Enter three known values and the tool cross-multiplies to return the missing fourth term — perfect for ratio homework, recipe scaling, and map distance problems.
What is the Proportion Calculator?
All cross-multiplication runs locally in your browser. Your homework ratios and business calculations stay completely private.
When to use a proportion calculator
- Math homework — solve ratio and proportion word problems quickly
- Recipe scaling — adjust ingredient amounts when serving size changes
- Map and model scales — convert distances using a known scale factor
- Finance and statistics — find an unknown value in a proportional relationship
How the Proportion Calculator works
Enter A, B, and C in the input fields representing the proportion A : B = C : X. The tool computes X = (B × C) ÷ A using cross-multiplication. If A is zero, the result is undefined and the tool displays a dash instead of a number.
How to solve a proportion
- Identify your three known values from the proportion A/B = C/X.
- Enter A, B, and C in the corresponding fields.
- Click Calculate to find the unknown X.
- Verify the result by checking that A/B equals C/X.
ToolsPopper vs Calculator.net
- Rule-of-three focus — direct A : B = C : X layout without extra modes
- Unlimited free use — no throttled sessions or account walls
- 100% private — ratio values processed on your device only
- No signup — solve proportions immediately
- Mobile-friendly — four fields and one button for quick homework checks
More free calculators on ToolsPopper
Proportion Calculator works even better alongside our other utilities. Try Inches to mm Converter, 3×3 Matrix Inverse Calculator and GCD & LCM Calculator — every tool in our Calculators collection is free, runs without signup, and keeps your data private.