Percentage Calculator

Example Calculation

• What is 15% of 200? 200 x 15 / 100 = 30.
• 45 is what percent of 60? 45 / 60 x 100 = 75%.
• Percent change from 80 to 100? (100 − 80) / 80 x 100 = +25%.
• Decrease 250 by 30%? 250 x 0.70 = 175.

Note that going from 100 back down to 80 is a 20% decrease, not 25%, because the base number is different.

How It Works

Percentages show up everywhere: sale prices, tips, tax, interest rates, grades, nutrition labels and business metrics. This percentage calculator covers the four problems people solve most often, and you pick the one you need from the dropdown. The fields below update instantly, so you can experiment with different numbers.

Mode 1: What is X% of Y? Use this for discounts, tips and commissions. For example, 15% of 200 is 30. Mode 2: X is what percent of Y? Use it for test scores or market share: 45 out of 60 is 75%. Mode 3: Percent change from X to Y tells you how much a value rose or fell relative to its starting point — useful for price changes, salary raises and stock moves. Mode 4: Increase or decrease Y by X% gives you the new value after applying a percentage change, such as a 20% markup or a 30% discount.

Percent change is always measured relative to the original number, which is why increases and decreases are not symmetrical. If a price rises 50% and then falls 50%, you end up below the starting price: 100 becomes 150, then 75. Similarly, going from 80 to 100 is a 25% increase, but going from 100 back to 80 is a 20% decrease.

A few quick mental shortcuts: 10% is the number with the decimal point moved one place left; 5% is half of that; 1% is the decimal moved two places. To calculate 15%, add 10% and 5%. Use this tool to confirm your mental math or when you need several decimal places of precision. Also be careful to distinguish percentage points from percent: an interest rate moving from 4% to 5% is a one percentage-point change but a 25% relative increase.

Formula Explained

X% of Y: Y × X ÷ 100. X is what % of Y: X ÷ Y × 100.

Percent change: (new − old) ÷ |old| × 100. Increase by X%: Y × (1 + X/100); decrease: Y × (1 − X/100).

Assumptions and limits

• Percent change is measured against the original number, so an increase and a decrease of the same percent do not cancel out.
• The percent change from zero is undefined, so the tool asks for a non-zero starting value.
• Results are shown to four decimal places and rounded.