Solve any percentage problem: X% of Y, percent change and more.
What is a percentage? A percentage is a way of expressing a number as a fraction of 100. It makes comparisons easy — from discounts and tips to test scores and interest rates.
1. What is X% of Y?
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2. X is what % of Y?
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3. Percentage change from X to Y
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Tip: calculate first — your result is included when you share.
📚 Related guide:How to Calculate Percentage Increase and Decrease — one formula for increases and decreases, worked price, salary and discount examples, and percentage points vs percent explained.
📚 Related guide:How to Convert Percentage to GPA — the ÷9.5 rule for 10-point scales, 4.0-scale bands, a worked example, and how to pick the right formula.
How to Use the Percentage Calculator
Percentages are everywhere: discounts, tips, exam marks, salary hikes, tax and interest rates. Yet the three basic percentage questions trip people up surprisingly often. This calculator answers all three instantly, with the working shown so you can double-check.
"What is X% of Y?" — the discount question. Example: 20% off a 150 bill. The maths is (X ÷ 100) × Y. "X is what percent of Y?" — the marks question. Example: you scored 30 out of 150. The maths is (X ÷ Y) × 100. "Percentage change from X to Y" — the growth question. Example: your salary rose from 100 to 120. The maths is ((Y − X) ÷ X) × 100.
The most common mistake is mixing up the second and third types. "30 is what percent of 150?" (answer: 20%) is not the same as "what is the percent change from 30 to 150?" (answer: +400%). The calculator labels each mode clearly so you always pick the right one.
Two mental-math tricks for daily life: to find 10% of anything, just move the decimal point one place left (10% of 850 = 85). To add X% to a price, multiply by (1 + X/100) — e.g. adding 15% tip means × 1.15. For bill-splitting with tips built in, our Tip Calculator is even faster.
Frequently Asked Questions
How do I calculate X percent of a number?
Multiply the number by X and divide by 100. For example, 20% of 150 = (20 ÷ 100) × 150 = 30.
How do I find what percent one number is of another?
Divide the first number by the second and multiply by 100. For example, 30 is (30 ÷ 150) × 100 = 20% of 150.
How do I calculate percentage increase?
Subtract the old value from the new value, divide by the old value, and multiply by 100. From 100 to 120: ((120−100) ÷ 100) × 100 = 20% increase.
What is the difference between percent and percentage point?
A change from 20% to 25% is a 5 percentage-point increase, but a 25% relative increase (5 ÷ 20). News headlines sometimes blur the two — now you know the difference.
How do I reverse a percentage? e.g. price after 20% off is 80 — what was it?
Divide by (1 − rate): 80 ÷ 0.8 = 100. To reverse an X% increase, divide by (1 + X/100).
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