Percentage calculator
Percentage of a number
Result
One number as %
Percentage
Percentage change
Percentage change
Add or subtract %
New value
Decimals: 12.5 or 12,5. Leave out thousands separators.
How percentage calculations work
A percentage means “out of 100”. For example, 20% is 20 out of every 100, or 0.2. Choose the question that matches what you know and what you want to find.
Find a percentage of a number
Use this when you know the percentage and the full amount. It can help you find a discount, a deposit, a tip or a share of a total.
Result = (Percentage ÷ 100) × Number
- Divide the percentage by 100 to turn it into a decimal.
- Multiply that decimal by the full amount.
20% of 250: 20 ÷ 100 = 0.2, then 0.2 × 250 = 50.
This gives the portion itself. For a 20% discount on 250, the saving is 50 and the price after the discount is 200. Use the add or subtract question to find that final amount directly.
Find what percentage one number is of another
Use this when you know a part and the total, such as a score out of the maximum possible score or the amount of a target already reached.
Percentage = (Part ÷ Total) × 100
- Divide the part by the total.
- Multiply by 100 to express the share as a percentage.
50 out of 250: 50 ÷ 250 = 0.2, then 0.2 × 100 = 20%.
The order matters: the first value is the part and the second is the total. The total cannot be zero. A part larger than the total gives a result above 100%, which can be valid when comparing values.
Calculate a percentage increase or decrease
Use this to compare a new value with its starting value. The starting value is the reference, so reversing the two numbers changes the answer.
Change (%) = ((New value − Starting value) ÷ Starting value) × 100
- Subtract the starting value from the new value.
- Divide the difference by the starting value.
- Multiply by 100. A positive result is an increase; a negative result is a decrease.
From 200 to 250: the difference is 50. Then 50 ÷ 200 × 100 = 25%, an increase. From 250 to 200, the result is −20%, a decrease.
The starting value must be greater than zero for this calculator. Going from zero to another value has no finite percentage change under this formula. If both positive values are equal, the change is 0%.
Add or subtract a percentage
Use this when you want the final amount after an increase or reduction, rather than just the size of the increase or reduction.
New value = Starting value × (1 + Percentage ÷ 100), or × (1 − Percentage ÷ 100)
- Choose plus for an increase or minus for a reduction.
- Find the percentage of the starting value.
- Add that amount to the starting value, or subtract it.
250 plus 20%: 250 × 0.2 = 50, so 250 + 50 = 300. With minus selected, 250 − 50 = 200.
An increase and a decrease by the same percentage do not cancel each other when applied in sequence. Increasing 100 by 20% gives 120; reducing 120 by 20% gives 96. Each calculation uses its own starting value.
Reading and checking your result
- Each question works independently. Results update when both values are valid; Calculate or Enter also checks the fields. Clear resets only that question.
- Under Options, choose how many decimal places to show. A rounded answer carries the ≈ symbol. Extra precision changes the displayed rounding, not the formula.
- Use a decimal point or comma, without thousands separators. Inputs support up to 24 whole-number digits and 12 decimal places. Copy uses the selected precision.
- A percentage change is different from a percentage-point difference. Moving from 20% to 25% is an increase of 5 percentage points, but a relative increase of 25%: (25 − 20) ÷ 20 × 100.