Ratio Calculator
Simplify a ratio, scale it up or down, or solve a proportion (find a missing value where two ratios are equal).
Inputs
Optional. If filled with D blank, calculator solves for D.
Leave 0 to solve for D given A, B, C.
Simplified ratio (A:B)
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As decimal (A÷B)
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As percent
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D in proportion A:B = C:D
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About Ratio Calculator
Simplifying ratios
Divide both sides by their greatest common divisor (GCD). 12:18 simplifies to 2:3 because GCD(12,18) = 6.
Solving proportions
If A:B = C:D, then A × D = B × C. Solve for the unknown: D = B × C ÷ A. This calculator does that automatically when D is left blank or zero.
Real-world use
Scaling recipes, computing fuel mixtures, comparing population densities, working with map scales, computing aspect ratios for screens or photos.