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Home › Everyday › Proportion Calculator

Proportion Calculator

By the CalcMundi team · Updated October 22, 2026 · Formulas checked against standard financial math

Enter the three values you know and get the fourth. Works for recipes, prices, scaling, speed and more.

Direct proportion

Both values grow together. If 3 lb cost $12, how much do 5 lb cost? X = 12 × 5 ÷ 3 = $20.

Inverse proportion

One goes up as the other goes down. If 3 workers need 12 days, 5 workers need X = 3 × 12 ÷ 5 = 7.2 days.

Frequently asked questions

Direct or inverse?

Ask: if A doubles, does B double too? Then it is direct. If B halves, it is inverse.

See also

Gas Cost CalculatorFuel cost for your trip, split per personSquare Footage CalculatorArea of rooms, floors and lotsPaint CalculatorGallons of paint for your roomElectricity Cost CalculatorWhat each appliance adds to your bill

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Results are estimates for information only and are not financial, legal or medical advice. Rates, taxes and fees vary — confirm with a professional or your lender.