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Free calculators with published formulas. Pick a tool, enter numbers, get a result — all in your browser.

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24 tools online. Each page shows the formula and a worked example.

Find X% of a number, or what percent one number is of another.

Percent increase or decrease between two values.

Arithmetic mean of a comma-separated list of numbers.

Simplify a:b and scale a ratio to a target total.

Principal square root of a non-negative number.

Area and circumference from radius.

Area from base and height.

Find the missing side of a right triangle.

Body Mass Index from height and weight (metric).

Basal metabolic rate (Mifflin–St Jeor).

Devine formula ideal body weight.

Split a bill with tip across any number of people.