Percentage Calculator

How to Calculate a Percentage

A percentage is a number expressed as a fraction of 100. The word "percent" literally means "per hundred." Percentages are everywhere — discounts, grades, tips, interest rates, statistics — making this one of the most practically useful calculations in everyday life.

% of a Number — Find the Part

To find what X% of a number is, multiply the number by X and divide by 100. For example, 20% of 350 = (350 × 20) ÷ 100 = 70. This is the most common percentage question — used for discounts, tips, and tax calculations.

What % Is X of Y? — Find the Rate

To find what percentage one number is of another, divide the part by the whole and multiply by 100. Example: 45 is what percent of 180? (45 ÷ 180) × 100 = 25%. Useful for grades, survey results, and proportions.

Percentage Change — Increase or Decrease

Percentage change measures how much a value grew or shrank relative to its starting point. Formula: ((New − Old) ÷ Old) × 100. Example: from 80 to 96 → ((96 − 80) ÷ 80) × 100 = +20%. A positive result is an increase; negative is a decrease.

Percentage vs. Percentage Points

These are often confused. If an interest rate rises from 2% to 3%, that's a 1 percentage point increase — but a 50% percentage change. The percentage change tells you how big the shift is relative to where you started.

Common Percentage Landmarks

Some percentages are worth memorizing: 50% = one half, 25% = one quarter, 75% = three quarters, 10% = one tenth (easy to calculate by moving the decimal point one place left), 1% = one hundredth. Knowing these makes mental estimation much faster.