Free Percentage Calculator
Four percentage calculators in one — instant results as you type.
What is X% of Y?
X is what percent of Y?
Percentage change from X to Y
X is Y% — what is 100%?
🔒 All calculations happen in your browser. No data is ever sent to a server.
How It Works
Choose the type of percentage problem
All four calculators are ready on this page.
Enter your numbers
Results appear instantly as you type — no button to click.
Use or copy the result
Grab it with one click on the Copy button.
Four Ways to Solve a Percentage Problem
Most percentage questions people search for fall into one of four shapes, and each one needs a slightly different formula. The first calculator above answers "what is X% of Y?" — the question behind tips, sales tax, and discounts. Multiply the number by the percentage divided by 100: result = (percentage ÷ 100) × number. A 15% tip on a $200 dinner is 0.15 × 200 = 30.
The second calculator flips that question around: "X is what percent of Y?" — useful for grades, completion rates, or market share. Divide the part by the whole and multiply by 100: result = (part ÷ whole) × 100. Getting 45 questions right out of 180 is (45 ÷ 180) × 100 = 25%.
Percentage change is a different question entirely — it's not "what portion is this," it's "how much did this move." Comparing a salary that went from $80,000 to $100,000 needs ((new − original) ÷ |original|) × 100, which gives a 25% increase. The same formula flags decreases too — a value that drops always returns a negative result, so the calculator labels it clearly instead of leaving you to guess the sign. This is the formula behind year-over-year revenue growth, weight change, or price drops.
The fourth calculator solves the reverse-percentage problem: you know a partial value and what percentage it represents, and you need the original 100% figure. If a discounted price of $60 is 75% of the original, the original was 60 ÷ 0.75 = 80. This comes up constantly when working backward from a sale price, a partial payment, or a survey subgroup to the full total.
Beyond tips and discounts, these four formulas cover most everyday percentage work: sales tax, grade calculations, salary raises, interest earned, population growth, and comparing statistics across time periods. Knowing which of the four shapes your problem fits is usually the hardest part — once you do, the arithmetic takes seconds.
Frequently Asked Questions
How do I calculate what percentage one number is of another?
Divide the part by the whole, then multiply by 100: (part ÷ whole) × 100. For example, if 45 out of 180 students passed a test, 45 ÷ 180 × 100 = 25%. Use the "X is what percent of Y?" calculator above to get this instantly.
How do I calculate percentage increase or decrease?
Subtract the original value from the new value, divide by the absolute value of the original, then multiply by 100: ((new − original) ÷ |original|) × 100. A positive result is a percentage increase; a negative result is a percentage decrease. Going from 80 to 100 is a 25% increase; going from 100 to 80 is a 20% decrease.
What is the formula for finding the original number from a percentage?
Divide the known value by the percentage it represents (expressed as a decimal): value ÷ (percentage ÷ 100). For example, if 60 is 75% of a number, the full number is 60 ÷ 0.75 = 80. This is useful for working backward from a discounted price or a partial result to the original total.
How do I calculate a tip or discount percentage?
For a tip, use "What is X% of Y?" with your bill total as Y and the tip percentage as X — an 18% tip on a $60 bill is 0.18 × 60 = $10.80. For a discount, the same formula gives you the amount saved; subtract that from the original price to get the sale price, or use the percentage change calculator to check the discount rate between two prices.
What is the difference between percentage and percentage points?
A percentage point is the simple arithmetic difference between two percentages, while a percentage change is that difference expressed relative to the starting value. If a rate goes from 20% to 25%, that's a 5 percentage point increase, but a 25% relative increase (5 ÷ 20 × 100). The two numbers look similar but mean very different things, especially with small base values.
How do I calculate percentage change between two years?
Use the "Percentage change" calculator with last year's figure as the original value and this year's figure as the new value. For example, if revenue went from $80,000 to $100,000, that's ((100000 − 80000) ÷ 80000) × 100 = 25% growth year over year.