Ratio Calculator
Solve ratio equations, scale ratios up or down, and compare two ratios easily.
Solve for Missing Value in A : B = C : D
Leave one field empty (or place 'x' in it) to calculate the missing value.
=
Understanding Ratios & Proportions
A ratio shows the relative sizes of two or more values. A proportion is an equation stating that two ratios are equal.
Solving Proportions:
If A / B = C / D, then A × D = B × C
Cross-Multiplication:
A = (B × C) / D
Scaling Ratios:
New Ratio = (A × Factor) : (B × Factor)
Frequently Asked Questions (FAQs)
To solve for an unknown value in a proportion like $A:B = C:D$, use cross-multiplication: multiply the diagonally opposite known values and divide by the remaining known value.
Scaling means multiplying or dividing both sides of the ratio by the same non-zero number to maintain the same proportion at a different total size.