Free Percentage Calculator
Calculate a percentage of a number, percentage increase or decrease, and the percentage difference between values.
Percentage Calculator
Percentages show up everywhere — pay raises, sale prices, tax rates, exam scores — and this calculator covers the three calculations people actually need most often: what a percentage of a number is, how much something increased or decreased, and the percentage difference between two values.
What are the three calculation modes, and what's the underlying formula?
"X% of Y" answers questions like what's 20% of 150; "X is what % of Y" answers what percent 30 is of 150; and "% change" answers how much a value grew or shrank between two numbers. All three trace back to the same core relationship: percentage = part ÷ whole × 100. These same calculations come up constantly outside personal finance too — prices, discounts, commissions, margins and taxes are all just percentages applied to a base number.
How do you calculate a percentage of a number, or add and subtract a percentage?
For X% of Y, convert the percentage to a decimal and multiply by the number — 20% of 150 is 0.20 × 150 = 30. To find what percentage one number is of another, divide the first number by the second and multiply by 100 — 30 is what percent of 150 works out to (30 ÷ 150) × 100 = 20%. To add or subtract a percentage from a number, calculate that percentage of the original value first, then add or subtract the result from the original.
How do you calculate percentage increase, decrease and change?
Percentage increase: subtract the original value from the new value, divide by the original value, and multiply by 100. Percentage decrease uses the same steps in the other direction — subtract the new value from the original, divide by the original, multiply by 100. Percentage change is the general version of both: (new − original) ÷ original × 100, where a positive result means an increase and a negative result means a decrease.
What's the difference between percentage change and percentage points?
Percentage change is relative to the starting value — going from 10% to 12% is a 20% increase, since 2 is 20% of the original 10. Percentage points measure the raw gap between the two figures instead — the same move from 10% to 12% is simply 2 percentage points, a much smaller-sounding number for the exact same change, which is why headlines sometimes pick whichever framing sounds more dramatic.
What's the difference between percentage change and percentage difference?
Percentage change assumes one of the two values is the original or baseline you're measuring from; percentage difference compares two values without treating either one as the baseline, so the right formula depends on what you're actually trying to express. A percentage discount is a specific case of percentage change: multiply the original price by the discount percentage to get the amount saved, then subtract that from the original price to get the final price.
Where does the % symbol itself come from?
"Percent" comes from the Latin per centum, "by the hundred," filtered through the Italian merchant term per cento — "for a hundred" — used across Italian city-states from at least the 1400s as trade and banking expanded and merchants needed a fast shorthand for profits, interest and losses. The earliest known written abbreviation, from a manuscript dated around 1425-1435, shows "pc" with a small loop standing in for the Italian ending "-o." Over the next two centuries the abbreviated "p" was dropped entirely and "cento" contracted down to two circles separated by a horizontal line — the modern % symbol was recognizably in use in Italian and European mathematical texts by the 1600s, essentially unchanged from what's printed on a receipt today.
Is Percentage Calculator free to use?
Yes. Percentage Calculator is completely free, with no sign-up and no usage limits.
Do I need to install any software?
No. Percentage Calculator runs directly in your web browser — nothing to download or install.
Is my data kept private?
Everything happens on your device. We never receive or store the file or text you enter into Percentage Calculator.