Proportions Calculator
Solve a/b = c/d (leave one blank)
Check Proportionality
Formula
a/b = c/d → a×d = b×c
Frequently Asked Questions
How do I solve a proportion?
Cross-multiply: if a/b = c/d, then a×d = b×c. To find d: d = (b×c)/a. For example, 3/4 = 9/d: d = (4×9)/3 = 12.
You may also need
+
Ratio Calculator
Free ratio calculator. Solve proportions, simplify ratios, and scale ratios up or down. Perfect for recipes, maps, and math problems.
Math%
Percentage Calculator
Free online percentage calculator. Find percentages, percentage change, percentage difference, and more. Fast, accurate, no signup required.
Math+
Fraction Calculator
Free fraction calculator. Add, subtract, multiply, and divide fractions. Simplify fractions and convert between fractions and decimals.
Math