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Module · Math · Scientific
Ratio Calculator
Simplify ratios, scale up or down, and find the missing term in a proportion (A : B :: C : D).
Proportion A : B = C : D
Solve for
Missing term (D)
12
A : B simplified
3 : 4
A / B (decimal)
0.75
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Guide
How Ratio Calculator works
Step 01
Enter three values
Leave the term you want to find as any placeholder.
Step 02
Choose solve-for
A, B, C or D.
Step 03
See answer
Cross-multiplication finds the missing term plus a simplified A:B.
FAQ
Frequently asked
Cross-multiplication?+
If A/B = C/D, then A × D = B × C. Solve for whichever is unknown.