Percentage calculator
Pick the percentage formula you need, enter your numbers, and get the result instantly — no formula memorisation required.
What is X% of Y?
About this tool
Percentages are simple arithmetic that people get wrong in predictable ways, usually because the base is ambiguous. A 20% discount followed by a 10% discount is not 30% off — it is 28%, because the second discount applies to the already-reduced price. A price cut by 50% and then raised by 50% does not return to where it started; it ends 25% below. And a value that falls by 40% needs to rise by 67% to recover, not 40%, because the base has changed. The other persistent confusion is between percentage points and percent. An interest rate moving from 2% to 3% has risen by one percentage point and by fifty percent, and financial reporting that blurs the two is either careless or deliberate. These distinctions matter in discounts and markups, tax and VAT calculations, tips, commission, interest, and any figure comparing one period to another. This calculator covers the four operations that come up most: X percent of Y, what percentage X is of Y, percentage change between two values, and adding or subtracting a percentage from a number.
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Choose the type of percentage calculation: percentage of a number, percentage change, or what percentage one number is of another.
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Enter your values — the result updates instantly.
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Use the percentage increase/decrease mode to calculate discounts, tax, or growth rates.
Calculate discounts, tips, and tax amounts on prices.
Find the percentage change between two values for reports or dashboards.
Determine what percentage one number is of another for data analysis.
Percentage of a number
15% of 20030Percentage change
From 80 to 10025% increaseWhat percent
45 is what % of 18025%Stacked discounts do not add up
Cause: Each percentage applies to a different base. The second discount is calculated on the price after the first, so the combined effect is always less than the sum.
Fix: Multiply the remaining fractions instead of adding the discounts: 20% and 10% off gives 0.8 x 0.9 = 0.72, so 28% off. Apply each step in sequence rather than combining first.
Percentage increase and decrease are not symmetric
Cause: The base changes between the two operations. A decrease is measured against the original value and the subsequent increase against the reduced one.
Fix: To reverse a decrease of p percent, increase by p / (100 - p) x 100 percent. A 40% fall needs a 66.7% rise to get back to the starting value.
Removing tax by subtracting the tax percentage
Cause: Tax was added to the net price, so it is a percentage of the net, not of the gross. Subtracting 20% from a VAT-inclusive price undershoots the correct net figure.
Fix: Divide rather than subtract: net = gross / 1.20 for a 20% rate. Subtracting 20% from a gross price of 120 gives 96, whereas the correct net is 100.
These answers explain common percentage calc tasks, expected input formats, and edge cases so both visitors and search engines can understand what this tool does.
How do I calculate X% of Y?
Multiply Y by X and divide by 100. For example, 20% of 150 = (150 × 20) / 100 = 30.
How do I calculate percentage change?
Percentage change = ((New − Old) / |Old|) × 100. A positive result is an increase; negative is a decrease.
How do I find what percentage X is of Y?
Divide X by Y and multiply by 100. For example, 30 is what % of 150? = (30 / 150) × 100 = 20%.
How do I calculate a discount amount?
Use the 'What is X% of Y?' calculator. Enter the discount percentage as X and the original price as Y. The result is the amount to subtract from the price. For example, 20% of 500 = 100, so the discounted price is 400.
How do I calculate percentage increase or decrease?
Use the percentage change calculator. Enter the original value and the new value. A positive result means an increase; a negative result means a decrease. For example, going from 80 to 100 is a 25% increase.