Percentage Calculator

Calculate any everyday percentage

Use this percentage calculator for the four questions that come up most often: finding a percentage of a number, finding what percentage one number is of another, working out a percentage increase or decrease, and reversing a percentage to find the original number. Choose the question that matches yours, enter the two values, and the answer updates immediately.

The calculation runs in your browser. The values can be included in the page address so you can share a calculation, but they are not sent away for the calculation itself.

What is X% of Y?

To find a percentage of a number, divide the percentage by 100 and multiply it by the number:

X% of Y = (X ÷ 100) × Y

For example, to find 15% of 80:

(15 ÷ 100) × 80 = 12

This is useful for discounts, tips, sales tax, commission, and working out a portion of a total. If a $80 item is 15% off, the discount is $12; subtract it from the original price to get $68.

X is what percent of Y?

To express one number as a percentage of another, divide the first number by the second and multiply by 100:

(X ÷ Y) × 100

For example, if 18 of 60 questions are correct:

(18 ÷ 60) × 100 = 30%

The second number is the whole, baseline, or total. It cannot be zero, because a percentage of zero is undefined.

X is Y% of what?

This is the reverse-percentage question. You know a part and its percentage, and need to recover the whole:

X ÷ (Y ÷ 100)

For example, if $45 is 15% of a budget:

45 ÷ (15 ÷ 100) = 300

The budget is $300. This is helpful when a report gives a share but not its total, or when you know the sale amount and discount percentage. It does not work for 0%: zero percent of every possible total is zero, so there is no single original number to find.

Percentage change from X to Y

Percentage change compares the difference with the starting value:

((Y − X) ÷ |X|) × 100

For example, a price rising from $120 to $150 changes by:

((150 − 120) ÷ 120) × 100 = 25%

A positive answer is an increase; a negative answer is a decrease. The starting value cannot be zero because there is no meaningful percentage change from zero. If the starting value is negative, the calculator uses its magnitude as the comparison base so the direction still reflects whether the value moved up or down.

Percentage points are not percentage change

These phrases sound similar but mean different things. If a rate rises from 20% to 25%, it increases by 5 percentage points. Relative to the original 20%, it is a 25% increase, because 5 ÷ 20 = 0.25.

Use percentage points when comparing two rates directly, such as interest rates, poll results, or conversion rates. Use percentage change when comparing how large the movement is relative to where it started.

Frequently asked questions

How do I calculate a percentage of a number?

Convert the percentage to a decimal and multiply it by the number. For example, 25% of 200 is 0.25 × 200 = 50. In the calculator, choose What is X% of Y?, enter 25 for X and 200 for Y.

How do I find what percent one number is of another?

Divide the first number by the second, then multiply by 100. For example, 30 is what percent of 120? 30 ÷ 120 × 100 = 25%. Choose X is what percent of Y? to do this directly.

How do I find the original number from a percentage?

Divide the known part by the percentage written as a decimal. If 25 is 10% of a number, the number is 25 ÷ 0.10 = 250. Choose X is Y% of what? in the calculator. A percentage of zero cannot identify an original number, because every number has 0% equal to zero.

How is percentage change calculated?

Subtract the starting value from the ending value, divide by the starting value, then multiply by 100. Moving from 80 to 100 is (100 − 80) ÷ 80 × 100 = 25%, so it is a 25% increase. A negative result means a decrease.

Why is a decrease from 100 to 50 not cancelled by an increase from 50 to 100?

Percentages use their starting value as the base. Dropping from 100 to 50 is a 50% decrease, but going from 50 back to 100 adds 50 on a base of 50, which is a 100% increase. Equal percentage increases and decreases do not usually cancel out.