Three everyday percentage questions, one tool.
A percentage calculator handles the everyday percent questions in one place: what is X% of a number, what percent one number is of another, and the percentage increase or decrease between two values.
Most percentage problems are one of three forms. 'What is X% of Y' multiplies Y by X/100. 'X is what percent of Y' divides X by Y and multiplies by 100. 'Percent change from A to B' is (B − A) ÷ A × 100, positive for an increase, negative for a decrease. Recognizing which form you have is most of the battle; the calculator applies the right one automatically.
Raising a rate from 4% to 5% is a one percentage-point increase but a 25% relative increase, and mixing these up causes real confusion, especially with interest rates, tax rates, and statistics. Likewise, a 50% drop followed by a 50% rise doesn't return to the start (it lands at 75% of the original), because each percentage applies to a different base. Being explicit about the base a percentage refers to avoids these mistakes.
Multiply the number by the percentage divided by 100. For example, 20% of 150 is 150 × 0.20 = 30.
Divide the first by the second and multiply by 100. So 30 out of 150 is 30 ÷ 150 × 100 = 20%.
Subtract the old value from the new, divide by the old value, and multiply by 100. A rise from 40 to 50 is a 25% increase.
See the exact formula and a worked example on our methodology page.