Five percentage calculators with the working shown. Runs on your device.
Each question has its own tab. X% of Y finds a part of a number: 15% of 80 = 12. X is what % of Y finds the share one number is of another: 12 is 15% of 80. Change from X to Y finds how far a value moved, with a plus or minus sign for the direction: 80 to 100 is +25%. Difference between X and Y compares two values when neither one is the starting point: 80 and 100 differ by 22.222222%. Add or subtract a % changes a number by a percentage, and can also find the original number before that change: 80 plus 15% is 92. Every answer comes with its formula in words and its working with the numbers in place, so you can check it by hand.
A percent change divides by the size of the starting value, so the answer depends on which number you start from. Going from 100 to 200 is +100%, but going from 200 to 100 is -50%, because the same gap of 100 is 100% of 100 and 50% of 200. The tool divides by the size of the start, not by its sign. A start of -50 counts as 50 in the divisor, so going from -50 to -25 is +50%: the value rose by 25, and 25 is half of 50. Going from -50 to 25 is +150%. A start of 0 cannot be used, because nothing can be divided by zero, and the tool says so instead of showing an answer.
Adding 15% to 80 gives 92. To get back to 80 from 92, divide by 1.15. Taking 15% off 92 gives 78.2, which is not 80. Choose Add or subtract a %, pick Increase or Decrease, and set Find to The original value. For a discount, a price of 68 after 15% off came from 80, because 68 ÷ (1 - 0.15) = 80. A 15% fall followed by a 15% rise does not return to the start either: 100 falls to 85, and 85 rises to 97.75.
The tool does its arithmetic with exact decimal fractions, not with binary floating-point numbers, which can leave a small wrong digit at the end of a result. So 0.1 to 0.3 is exactly +200%, and 0.1 plus 200% is exactly 0.3. Each number can have up to 15 digits before the decimal point and up to 10 after it. Commas as thousands separators are accepted in the input, as in 1,234.5. Answers are rounded to 6 decimal places, with halves rounded away from zero, and the line Rounded to 6 decimal places appears when that happened. Answers have no thousands separators. The tool does not handle currency, compound growth or percentage points.
Multiply the number by the percentage divided by 100. For 15% of 80, that is 0.15 × 80 = 12. Choose X% of Y, type 15 and 80, and the answer 12 appears with the working under it, so you can check the steps by hand.
Percentage difference is symmetric. It compares two values with neither one as the starting point, so 80 and 100 differ by 22.222222% whichever is typed first. Percent change has a starting value. The change from 80 to 100 is +25%, and the change from 100 to 80 is -20%. Use Change from X to Y when one number is the old value and the other is the new one.
No. A percentage point is the plain difference between two percentages. If a rate moves from 10% to 15%, it has gone up 5 percentage points, and that is a +50% change in the rate. In Change from X to Y, type 10 and 15: the answer is +50% and the Difference tile shows +5, the change in points.
Because the decrease is taken from a larger number. 100 rises 20% to 120, but 120 falls 20% only to 96, not back to 100, since 20% of 120 is 24. Going from 120 back to 100 is a decrease of 16.666667%. To find the original before a 20% increase, choose Add or subtract a %, pick Increase and The original value.
Choose Add or subtract a %, pick Decrease, and set Find to The original value. Type the discounted price as the number and the discount as the percent. A price of 68 after 15% off was 80, because 68 ÷ (1 - 0.15) = 80. Use 15 as the percent, not 0.15.
A percent of 0 is 0, and the difference between 0 and 10 is 200%. The tool refuses a 0 as the whole in X is what % of Y, because that divides by zero. It also refuses 0 as the starting value in a percent change, and both numbers at 0 in a percentage difference. Each refusal says which number to change.
No. The numbers you type stay in this tab and are never sent or saved. Only the tab you chose and the Increase or Decrease and Find settings are remembered on this device. The page counts visits with Google Analytics. It sends the tool's name, how you reached the page, whether an answer appeared or was copied, and a rough time bucket. It never sends the numbers, the answers or your settings.