Percentage Calculator

How to Use the Percentage Calculator

Choose a calculation mode using the three buttons at the top, then enter your numbers in the input fields. The result appears instantly along with a formula explanation showing the exact calculation performed.

"What is X% of Y?" — Enter the percentage in the X field and the total value in the Y field. For example, entering 15 and 200 calculates 15% of 200, which is 30. This is useful for calculating tips, discounts, tax amounts, or commission values.

"X is what % of Y?" — Enter the partial value in X and the total in Y. For example, 45 is what percent of 180? The answer is 25%. Use this to find test scores, completion percentages, or market share.

"% change from X to Y" — Enter the starting value in X and the ending value in Y. The calculator shows the percentage increase or decrease. For example, a price changing from 80 to 100 is a 25% increase. A change from 100 to 75 is a 25% decrease.

Percentage Formulas Explained

Understanding the math behind percentages helps you verify results and use the formulas in spreadsheets or code.

X% of Y: Multiply Y by X divided by 100. result = (X / 100) × Y. This is the most fundamental percentage operation. "Percent" literally means "per hundred" — so 20% means 20 per 100, or 0.20 as a decimal.

X is what percent of Y: Divide X by Y and multiply by 100. result = (X / Y) × 100. This converts a ratio into a percentage. If you scored 42 out of 60 on a test, that is (42 / 60) × 100 = 70%.

Percentage change: Subtract the old value from the new value, divide by the absolute value of the old value, and multiply by 100. result = ((new − old) / |old|) × 100. A positive result indicates an increase; a negative result indicates a decrease. Using the absolute value of the old number in the denominator correctly handles cases where the starting value is negative.

Common mistakes to avoid: when calculating percentage change, always divide by the original (old) value, not the new one. And when someone says a price "dropped by 50% then went up by 50%," those do not cancel out — a 50% drop followed by a 50% increase results in only 75% of the original value. The percentage calculator correctly handles all of these scenarios.

Percentages are used everywhere in daily life: sales tax (typically 5–12%), restaurant tips (15–20%), discounts (10–70%), interest rates (annual percentages on loans and savings accounts), grade calculations, voter turnout, and statistical data in news articles. Having a reliable percentage calculator at hand saves time and prevents errors in financial decisions.

Pre-Calculated Percentages

Looking for a specific percentage? Browse our pre-calculated percentage pages for instant answers to common queries like "what is 15% of 200" or "what is 20% of 500". Over 600 combinations are available with step-by-step explanations.

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