Percentage Calculator
CalculatorsFive percentage calculations in one place, each explained in a sentence.
Result
45
30% of 150 is 45.
(percent ÷ 100) × total
How this is calculated
What is X% of Y X / 100 x Y X is what percent of Y X / Y x 100 Change from A to B (B - A) / A x 100 Add or subtract X% from Y Y x (1 +/- X / 100) Difference between A and B |A - B| / ((A + B) / 2) x 100
How it works
A percentage is a fraction with 100 on the bottom. Every calculation here is that one idea rearranged: you either know the fraction and want the part, know the part and want the fraction, or want to describe how two numbers relate.
The distinction worth understanding is between percentage change and percentage difference. Change has a direction and a starting point, so it is not symmetric: 100 to 150 is a 50% increase, but 150 back to 100 is a 33.3% decrease. Difference is measured against the average of the two numbers, so it gives the same answer whichever way round you put them — 40% in that example. Using one when you mean the other is the single most common percentage error in business reporting.
A related trap: adding and then subtracting the same percentage does not return you to where you started. Add 20% to 1,000 and you get 1,200; take 20% off 1,200 and you get 960, not 1,000. The percentage is applied to a different base each time.
Worked example
Sales rose from 240 units to 312 units
- change = (312 - 240) / 240 x 100
- change = 72 / 240 x 100 = 30%
- For comparison, the symmetric difference:
- mean = (240 + 312) / 2 = 276
- difference = 72 / 276 x 100 = 26.09%
A 30% increase — or a 26.09% difference, depending on which you mean
How to use it
- Pick the calculation you need from the tabs.
- Enter the two numbers. The labels change to match the mode so it is clear which goes where.
- The result is restated as a sentence, so you can check it says what you meant.
Frequently asked questions
How do I calculate a percentage of a number?
Divide the percentage by 100 and multiply by the number. 30% of 150 is 0.30 x 150 = 45.
How do I work out what percentage one number is of another?
Divide the part by the total and multiply by 100. 45 out of 150 is 45 / 150 x 100 = 30%.
How do I calculate percentage increase?
Subtract the original from the new value, divide by the original, and multiply by 100. From 240 to 312: (312 - 240) / 240 x 100 = 30%.
What is the difference between percentage change and percentage difference?
Percentage change has a direction and is measured against the starting value, so it is not symmetric. Percentage difference is measured against the average of the two values and gives the same answer either way round. Reporting one as the other is a common mistake.
Why does adding 20% then subtracting 20% not return the original number?
Because each percentage is applied to a different base. 1,000 plus 20% is 1,200; 20% of 1,200 is 240, so subtracting it gives 960. To reverse a 20% increase you must divide by 1.2, not subtract 20%.
How do I calculate a percentage decrease?
Use the same formula as increase; a negative result is a decrease. From 150 to 100: (100 - 150) / 150 x 100 = -33.3%, meaning a 33.3% decrease.
How do I add a percentage to a price, such as GST?
Multiply by (1 + rate/100). Adding 18% to ₹1,000 gives 1000 x 1.18 = ₹1,180. To go the other way and strip tax out of an inclusive price, use the GST calculator, which handles the reverse correctly.
Related tools
- Discount CalculatorThe sale price, what you save, and what two discounts really add up to — in any currency.
- GST CalculatorAdd GST to a price or strip it out of one, with the correct CGST/SGST or IGST split.
- Conversion Rate CalculatorConversion rate, required traffic, lift — and whether your A/B result is real.
- Age CalculatorYour exact age in years, months and days — plus how long until your next birthday.
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Last updated 3 September 2026.