Percentage Calculator
Work out percentages in one step — find a percent of a number, see what percent one value is of another, or measure the change between two numbers. Results update instantly and never leave your browser.
Find a percentage of a number — for example, 25% of 200.
Percentage
Of value
Enter both numbers to see the result.
How to use Percentage Calculator
- 1
Choose a calculation
Pick % of to find a percentage of a number, Find % to see what percent one value is of another, or % change to compare two numbers.
- 2
Enter your two numbers
Type a value into each field. Commas and a stray percent sign are ignored, so 1,000 and 25% both work.
- 3
Read the result
The answer updates as you type. Percentage change also shows whether the move was an increase or a decrease.
- 4
Copy the answer
Copy the result with one click, ready to drop into a spreadsheet, a report, or a message.
The Math Behind Everyday Percentages
What a percent really means
The word percent comes from the Latin per centum, meaning "per hundred." A percentage is just a fraction with 100 as its denominator, so 25% means 25 out of 100, or the fraction 25/100, or the decimal 0.25. Converting between these three forms is the single skill that unlocks every percentage problem.
To turn a percent into a decimal, divide by 100, which is the same as moving the decimal point two places left, so 7% becomes 0.07. To go the other way, multiply by 100, so 0.4 becomes 40%. Once you are comfortable swapping between a percent and its decimal, the three calculations below are all variations on one multiplication.
Finding a percent of a number
The most common task is finding a percentage of a value. The formula is part equals percent divided by 100, times the whole. So 25% of 200 is 0.25 times 200, which is 50. A 15% tip on a 60 dollar meal is 0.15 times 60, or 9 dollars, matching the tool's "% of" mode.
A useful shortcut comes from the fact that percentages are reversible: x% of y always equals y% of x. That means 18% of 50 is the same as 50% of 18, which is just half of 18, or 9. Spotting these flips lets you do many percentage problems in your head before you ever reach for a calculator.
Finding what percent one number is of another
The second mode answers questions like "what percent is 50 out of 200?" The formula is part divided by whole, times 100. Here that is 50 divided by 200, which is 0.25, times 100, giving 25%. A student who scores 42 out of 56 on a test computes 42 divided by 56, times 100, for 75%.
This is the calculation behind grades, completion rates, and conversion rates alike. The key is identifying which number is the part and which is the whole: the whole is the total or the "out of" figure, and it goes in the denominator. The tool guards against the one impossible case, dividing by a total of zero, since you cannot take a fraction of nothing.
Percentage increase and decrease
Percentage change measures how much a value moved relative to where it started. The formula is the difference divided by the starting value, times 100. Going from 200 to 250, the difference is 50, divided by 200 is 0.25, so the increase is 25%. Going from 250 down to 200, the difference is still 50 but you divide by 250, giving a 20% decrease.
That asymmetry surprises people: the same 50-unit move is 25% up or 20% down depending on the starting point, because the base changes. The tool's "% change" mode handles both directions and labels each result as an increase, a decrease, or no change, so you never have to track the sign by hand.
Real scenarios where these come up
These three formulas cover most daily money math. A 20% discount on an 80 dollar jacket is 0.20 times 80, or 16 dollars off, leaving 64. Sales tax of 8% on a 50 dollar order is 0.08 times 50, or 4 dollars added. A tip, a markup, and a commission are all just "percent of a number."
Percentage change powers anything that grows or shrinks over time: a salary raise, a stock price move, year-over-year revenue, or a population trend. When a report says sales rose 12%, that is the difference divided by last period's figure. Recognizing which of the three modes a real question maps to is most of the battle.
Percentage points versus percent
One of the most common errors is confusing a percentage point with a percent. If an interest rate rises from 4% to 6%, it has gone up by 2 percentage points, but the percent increase is 2 divided by 4, which is 50%. These are two genuinely different statements about the same change, and mixing them up can be seriously misleading.
Use "percentage points" when you subtract two percentages directly, and "percent change" when you measure one relative to the other. Headlines often blur the two to make a change sound larger or smaller than it is. Knowing the difference lets you read the same number honestly and explain it precisely.
Why a discount and its reversal differ
A subtle trap is assuming a percentage increase and an equal decrease cancel out. They do not. Take 100, add 20% to get 120, then subtract 20% from 120: that removes 24, leaving 96, not 100. The second percentage acts on a larger base, so the round trip lands you short of where you began.
The same logic explains why you cannot undo a 25% markup with a 25% discount. To reverse a price that already includes a 20% increase, you divide by 1.20 rather than subtracting 20%. Whenever you chain percentage changes, apply each one to the running total, exactly as the change formula does, instead of adding and subtracting the percentages directly.
Frequently asked questions
How do I calculate a percentage of a number?
How do I find what percent one number is of another?
How is percentage change calculated?
What is the difference between percentage increase and decrease?
Does the calculator round results?
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