X percent of Y, what percent one number is of another, percentage increase or decrease, or reverse percentage - four calculations, instant and exact.
Nothing you enter is stored - this is pure arithmetic, computed and returned in the same request.
Four of the most common percentage calculations, in one tool: what X% of Y is, what percent one number is of another, the percentage increase or decrease between two numbers, and reverse percentage - working out what number X is Y% of. Pick the calculation, enter the two numbers, and the exact result updates instantly.
"What is X% of Y" answers questions like a 20% tip on a bill, or a 15% discount on a price. "X is what percent of Y" answers questions like a test score out of a total, or a budget spent against a total budget. "Percentage change from X to Y" answers questions like how much a price rose or a metric fell, as a percentage of the starting value. "X is Y% of what number" answers questions like a tax amount that is a known percentage of an unknown original price - working backward to find that original number.
20% of 50 is 10. 15 is 30% of 50. From 80 to 100 is a 25% increase, but from 100 back to 80 is a 20% decrease: percentage change is always measured against the starting number, so a rise and the fall that undoes it never have the same percentage. A 50% fall needs a 100% rise to get back to where it started.
When a rate moves from 4% to 5%, it rose by 1 percentage point, but by 25% of its starting value: enter 4 and 5 under percentage change to get the 25%. The two figures describe the same move, so a report should say which one it means.
Each calculation is a single fixed formula with exactly one correct answer, computed directly rather than estimated by a model. The displayed number is rounded to at most 6 decimal places, so a repeating result such as 1 as a percent of 3 reads 33.333333%. Inputs that would make a formula undefined are refused instead of returning an infinite result: a zero second number for "X is what percent of Y", a zero starting value for percentage change, and a zero percentage for reverse percentage. Inputs or results larger than 10^15 in absolute value are refused as well.
No. Neither number is written to disk, a database, a cache or a log. The site only counts which calculation ran, with no numbers attached.
A zero is accepted wherever it has a defined answer (e.g. 20% of 0 is 0). Where it would make the calculation undefined - a zero second number for 'X is what percent of Y', a zero starting value for percentage change, or a zero percentage for reverse percentage - the tool reports a validation error instead of a nonsensical result.
Yes, both fields accept negative numbers and decimals. Percentage change divides by the starting number as entered, sign included, so with a negative start the direction can look reversed: from -10 to -5 reads as a 50% decrease even though the number went up. If you are comparing losses or negative balances, check that this matches the convention your report uses.
The sign of the raw percentage change determines the direction, shown in plain words alongside the exact percentage so the result reads naturally rather than as a signed number.
To add 20% to 50, ask for 120% of 50: the answer is 60. To remove a 20% tax already included in a price of 120, use 'X is Y percent of what number?' with X = 120 and Y = 120: the price before tax is 100. Taking 20% off 120 would give 96, which is wrong.
Both start from the same profit but divide it by a different number. An item that costs 80 and sells for 100 makes a profit of 20: the margin is 20 as a percent of the price, 100, which is 20%; the markup is 20 as a percent of the cost, 80, which is 25%, the same as the percentage change from 80 to 100. To find the price that gives a 25% margin on a cost of 80, use 'X is Y percent of what number?' with X = 80 and Y = 75 (100 minus the margin): the answer is 106.666667. Adding 25% to the cost gives 100, which is only a 20% margin.
With the first number in A2 and the second in B2: X% of Y is =A2/100*B2, X as a percent of Y is =A2/B2*100, the percentage change from X to Y is =(B2-A2)/A2*100, and X is Y% of what number is =A2/(B2/100). If the result cell is formatted as a percentage, drop the *100, because that format multiplies by 100 for display: =A2/B2 with 15 and 50 shows 30%. Use this tool to check one row of a sheet by hand.
No, they compound: each percentage applies to the new number. A 10% rise on 100 is 110% of 100 = 110, and a second 10% rise is 110% of 110 = 121, so the total change from 100 to 121 is 21%. Stacked discounts work the same way: 10% off and then 20% off is 90% of 100 = 90, then 80% of 90 = 72, a 28% decrease from 100 to 72, not 30%. Run each step with 'What is X percent of Y?', then check the total with percentage change.
Percentage change measures against a starting number: from 80 to 100 is a 25% increase. Percentage difference compares two values with no before and after, such as two supplier quotes, and divides the gap by their average: the gap between 80 and 100 is 20, the average is 90, and 20 as a percent of 90 is 22.222222%. The tool has no separate mode for it: work out the gap and the average, then use 'X is what percent of Y?' with X = 20 and Y = 90.