How it works
This calculator answers the three everyday percentage questions: what is X% of a number, what percent one number is of another, and what the whole is when you know a part and its percent.
A percent is a fraction of 100, so 15% means 15/100 or 0.15. Every percentage problem is a rearrangement of one equation: part = percent × whole.
Formula
part = (percent ÷ 100) × whole; percent = part ÷ whole × 100; whole = part ÷ (percent ÷ 100)
Questions people ask
How do I find a percentage of a number in my head?
Find 10% by moving the decimal point one place left, then scale. For 15% of 200: 10% is 20, 5% is 10, so 15% is 30.
Is X% of Y the same as Y% of X?
Yes. Multiplication is commutative, so 8% of 50 equals 50% of 8. Both are 4. This is a handy shortcut for awkward percentages.
How do I find the original number before a percent was taken?
Use the "X is Y% of what" mode. If 30 is 15% of a number, divide 30 by 0.15 to get 200.