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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 personPercentage CalculatorPercent of, percent change, discountsDiscount CalculatorSale price, percent off and savingsTip CalculatorTip amount and bill split

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Free for blogs, real estate agents, brokers and any site. Paste this code where you want the calculator to appear. It adjusts its height on its own.

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.