Percentage calculator for everyday questions
Percentages come up everywhere: discounts, tips, tax, exam marks, price rises and growth. This percentage calculator answers the five most common questions in one place, with the result explained in plain words so you know it's the right one.
Percentage formulas
- X% of Y = Y × X ÷ 100. For example, 15% of 80 = 80 × 15 ÷ 100 = 12.
- X is what percent of Y = X ÷ Y × 100. For example, 12 ÷ 80 × 100 = 15%.
- Percent change = (new − old) ÷ old × 100. From 80 to 100: 20 ÷ 80 × 100 = 25% increase.
- Increase Y by X% = Y × (1 + X ÷ 100). Decrease = Y × (1 − X ÷ 100).
- X is P% of what = X ÷ P × 100. For example, 30 ÷ 20 × 100 = 150.
Questions
How do I calculate a percentage increase?
Subtract the old value from the new one, divide by the old value, and multiply by 100. Use the “Percent change” line above to do it automatically.
Is a 50% increase followed by a 50% decrease the same number?
No. 100 increased by 50% is 150, and 150 decreased by 50% is 75. Each percentage is taken of a different starting number.
How do I find the original price before a discount?
Use the last line: if you paid 80 after a 20% discount, you paid 80% of the original, so type “80 is 80% of what number” to get 100.