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UtilLab

Percentage Calculator

Three quick ways to calculate percentages: find a percentage of a number, find what percent one number is of another, or calculate a percentage change.

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Result

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Formula: Result = (Percent ÷ 100) × Number

Guide

Percentages: the three questions people actually ask

1. What is X% of Y?

Divide the percentage by 100 and multiply by the total.

result = (X ÷ 100) × Y

Example: a 15% discount on an 80-dollar item removes (15 ÷ 100) × 80 = 12 dollars, so you pay 68. Likewise an 18% tip on a 64.50 bill is 11.61.

2. X is what percent of Y?

Divide the part by the whole and multiply by 100.

percent = (X ÷ Y) × 100

Example: you answered 45 of 60 questions correctly, so your score is (45 ÷ 60) × 100 = 75%.

3. Percentage change from X to Y

Subtract the old value from the new one, divide by the old value and multiply by 100. A positive result is an increase, a negative one a decrease.

change = ((Y − X) ÷ |X|) × 100

Example: going from 80 to 100 is a +25% change. Going back from 100 to 80 is only −20%, because the base is different. This asymmetry is why "up 50%, then down 50%" does not return you to the start: 100 → 150 → 75.

Mistakes worth avoiding

  • Percent versus percentage points. If an interest rate moves from 4% to 5%, it rose by 1 percentage point, but by 25% in relative terms.
  • Using the wrong base. "Percent of what?" is the first question to ask. Margin is calculated on the selling price, markup on the cost.
  • Stacking discounts. A 20% discount followed by another 10% is a 28% total discount (0.8 × 0.9 = 0.72), not 30%.

Frequently Asked Questions

How do I calculate what percent X is of Y?
Divide X by Y and multiply by 100. For example, to find what percent 30 is of 150: (30 ÷ 150) × 100 = 20%. Use the second mode on this calculator to do this automatically.
How do I find X% of a number?
Multiply the number by the percentage divided by 100. For example, 20% of 150 = (20 ÷ 100) × 150 = 30. The first mode on this calculator does this for you instantly.
How do I calculate a percentage increase or decrease?
Subtract the original value from the new value, divide by the absolute value of the original, then multiply by 100. For example: from 80 to 100 → ((100 − 80) ÷ 80) × 100 = 25% increase. A negative result means a decrease.
What is the difference between percentage and percentage points?
A percentage point is an absolute difference between two percentages. If interest rates go from 2% to 5%, that is a 3 percentage point increase, but a 150% relative increase. This distinction matters when comparing rates, polls, or statistics.
Can I calculate percentage for any type of number?
Yes. The calculator works with any positive or negative decimal numbers. Results are shown with up to 4 decimal places for precision. All calculations run entirely in your browser — no data is sent to a server.