About the Percentage Calculator
This percentage calculator answers the six percentage questions people ask most: What is X% of Y? X is what percent of Y? X is Y% of what number? What is the percentage change from X to Y? And what do you get when you increase or decrease a number by a percentage? Pick the question, enter two numbers and the answer appears with a one-line explanation of the working.
It covers everyday situations — a 15% tip, a 30% off sale, a test score out of 80, a pay rise, a price increase, the share of a budget — as well as homework and spreadsheet checks. Each mode shows the formula in words so you can repeat it by hand or in Excel.
Percentages are just fractions of 100: 25% means 25 per 100, or 0.25. Percentage change is measured against the starting value, so going from 50 to 75 is a 50% increase, while going back from 75 to 50 is a 33.3% decrease.
With the default inputs, the result is 50. Change any value above to recalculate instantly.
How to use the percentage calculator
- 1Choose the question that matches your problem.
- 2Enter value X and value Y as labelled in the question.
- 3Read the result and the working line underneath.
- 4For price changes, use the increase/decrease modes to get the final amount directly.
Formula and method
A percentage is a ratio expressed per hundred, so every percentage problem comes back to the relationship Part = Percent/100 × Whole. Knowing any two of part, percent and whole lets you solve for the third: multiply to find a part, divide the part by the whole to get the percent, or divide the part by the percent (as a decimal) to recover the whole.
Percentage change compares the difference to the original value, using its absolute value so the sign always shows the direction. Increasing by P% multiplies by (1 + P/100) and decreasing multiplies by (1 − P/100), which is why a 20% rise followed by a 20% fall leaves you 4% below where you started.
- X, Y
- The two numbers entered (meaning depends on the question)
- P
- Percentage, e.g. 25 for 25%
- Old, New
- Starting and ending values for percentage change
Worked examples
What is 25% of 200?
25% is 25 per hundred, or 0.25. Multiply 0.25 × 200 = 50.
45 is what percent of 60?
Divide the part by the whole: 45 ÷ 60 = 0.75, then multiply by 100 to get 75%. A score of 45 out of 60 is 75%.
Price went from $80 to $92
The change is 92 − 80 = 12. Divided by the original 80 that is 0.15, a 15% increase.
18 is 30% of what number?
If 30% of the whole is 18, the whole is 18 ÷ 0.30 = 60.
Take 35% off $129.99
A 35% discount leaves 65% of the price: 129.99 × 0.65 = 84.49 (rounded to cents).
Frequently asked questions
How do I calculate a percentage of a number?+
Divide the percentage by 100 and multiply by the number. For 15% of 80, compute 0.15 × 80 = 12. Mentally, 10% is the number with the decimal moved one place, so 15% is 10% plus half of that.
How do I work out what percent one number is of another?+
Divide the part by the whole and multiply by 100. For example, 18 out of 24 is 18 ÷ 24 = 0.75, which is 75%.
How do I calculate percentage increase or decrease?+
Subtract the old value from the new value, divide by the old value and multiply by 100. From 50 to 65 is (65 − 50) ÷ 50 × 100 = 30% increase; a negative answer is a decrease.
What is the difference between percent and percentage points?+
Percentage points measure the simple difference between two percentages, while percent measures relative change. A rate rising from 4% to 5% is up 1 percentage point, which is a 25% increase.
Why doesn’t a 50% gain undo a 50% loss?+
Each percentage applies to a different base. $100 down 50% is $50, and 50% of $50 is only $25, so you end at $75. To recover a 50% loss you need a 100% gain.