Math calculators
Explore all 22 calculators in the Math category — available now, fast and free.
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About Math calculators
Math calculators cover the everyday and the technical: percentages and the rule of three, averages and statistics, geometry for area and volume, powers and roots, and unit conversions. Each shows the steps, not just the answer.
Frequently asked questions
How do I calculate a percentage of a number?
Multiply the number by the percentage and divide by 100 — for example 20% of 150 is 150 × 20 ÷ 100 = 30. The percentage calculator handles increases and decreases too.
How do I calculate a percentage increase or decrease?
Divide the difference between the new and old value by the old value, then multiply by 100 — a positive result is an increase, a negative one a decrease.
What is the rule of three?
The rule of three finds an unknown value from three known ones that are in proportion: if A relates to B as C relates to X, then X = B × C ÷ A.
How do I calculate the average of several numbers?
Add all the values and divide by how many there are; the statistics calculator also gives the median and standard deviation for a fuller picture.
How do I calculate the area of a shape?
Each shape has its own formula — a rectangle is length × width, a circle is π × radius² — and the geometry calculator picks the right one once you enter the dimensions.