Percentage Calculator
Calculate percentages - X% of Y, percentage change, increase/decrease.
Increase of 50.00%
Quick Reference
Multiple percentage calculators: what is X% of Y, X is what % of Y, percentage change between values, and increase/decrease by percentage. Quick reference table included.
Percentages show up everywhere — discounts, tips, tax, grades, markups, statistics, investment returns — but the mental math for even simple cases trips people up once there's a percent change involved. 'What's 17% of $84?' is easy with a calculator; 'my rent went from $1,800 to $2,100, what's the increase?' is a slightly different formula, and 'I got a 15% off coupon but the item was already marked up 20%' is a sequence people routinely get wrong.
This tool bundles the four percentage operations that cover 95% of real-world cases: X% of Y (straight percentage), X is what percent of Y (finding a rate from two numbers), percentage change between two values (increase or decrease), and applying an increase or decrease to a base (adding or subtracting a percent). Each takes two inputs and shows the formula used, so you can sanity-check the result.
Shoppers use it for sale prices, students for grade calculations, small-business owners for markup and margin, and analysts for growth rate reporting. It's also handy for reverse-percentage questions like 'the tipped bill was $36, what was the pre-tip amount?'
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Pick the percentage operation
Choose from: X% of Y, X is what % of Y, percentage change, or increase/decrease. Each has its own formula and inputs.
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Enter the two numbers
Fill in the two values the operation needs. Results update immediately — no submit button. Negative numbers and decimals are accepted.
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Copy or reuse
Copy the result for pasting into a spreadsheet or message. The formula is shown so you can verify or explain the calculation.
Sale price calculations
Find the actual price after a 30% discount, or reverse-calculate the original price from a sale tag that shows '40% off'.
Grade and score math
Figure out what score you need on a final to hit a target grade, or calculate the percentage you scored on a test with weighted sections.
Business markup and margin
Calculate selling price from cost plus markup, or find margin percentage from known cost and price — two different formulas people often confuse.
Growth rate reporting
Report month-over-month or year-over-year percentage change on metrics like revenue, traffic, or user counts without rewriting the formula each time.
What's the formula for percentage change?
(New value minus old value) divided by old value, times 100. So going from 80 to 100 is (100-80)/80 = 0.25 = 25% increase. Going from 100 to 80 is (80-100)/100 = -0.20 = 20% decrease. Note the denominator is always the starting value.
Why aren't a 20% increase and 20% decrease symmetric?
Because they're calculated from different bases. 100 increased by 20% is 120. But 120 decreased by 20% is 96, not 100. The second operation uses 120 as the base. To reverse a 20% increase you need a ~16.67% decrease.
What's the difference between markup and margin?
Markup is the increase from cost to price, expressed as a percentage of cost. Margin is the profit, expressed as a percentage of price. A 50% markup on a $10 item gives a $15 price, which is a 33% margin — same transaction, different denominators.
How do I apply two percentage changes in sequence?
Multiply the change factors. A 10% increase then a 5% discount is 1.10 × 0.95 = 1.045, i.e., a net 4.5% increase — not 5% as naive addition would suggest. The order doesn't matter if you're just multiplying factors.
Can percentages exceed 100%?
Yes. A doubling is a 100% increase, tripling is 200%. Percentage change isn't capped. What can't exceed 100% is the portion something represents of a whole — you can't have 120% of a pie unless you're using the word loosely.