Calculate percentages quickly with these three useful calculators.
A percentage calculator handles the three most common percentage problems people encounter in daily life: finding a percentage of a number, comparing two numbers as a percentage, and measuring how much something has changed over time.
Percentages show up everywhere: exam scores, discounts, tax rates, salary increases, nutrition labels, interest rates, and statistics. The math behind them is straightforward, but it is easy to get confused about which formula applies to which situation. This tool removes that confusion by separating the three calculation types so you always know you are using the right one.
Three calculators in one. Find a percentage of a number, work out what percent one number is of another, or calculate how much something has increased or decreased.
Use this when you know a percentage and want to find the actual value it represents.
How it works: Divide the percentage by 100, then multiply by the number.
Result = (Percentage ÷ 100) × Number
Example: What is 20% of 60? = (20 ÷ 100) × 60 = 0.20 × 60 = 12
Where you would use this:
Use this when you have two numbers and want to express the first as a percentage of the second.
How it works: Divide the first number by the second, then multiply by 100.
Percentage = (X ÷ Y) × 100
Example: 12 is what percent of 60? = (12 ÷ 60) × 100 = 0.20 × 100 = 20%
Where you would use this:
Use this when you want to measure how much something has changed between two values, expressed as a percentage.
How it works: Subtract the original value from the new value, divide by the original value, then multiply by 100. A positive result means an increase. A negative result means a decrease.
Percentage Change = ((New Value − Original Value) ÷ Original Value) × 100
Example: What is the percentage change from 40 to 50? = ((50 − 40) ÷ 40) × 100 = (10 ÷ 40) × 100 = 25% increase
Example: What is the percentage change from 80 to 60? = ((60 − 80) ÷ 80) × 100 = (−20 ÷ 80) × 100 = −25% (a 25% decrease)
Where you would use this:
Both use the same formula. The only difference is the direction of the result. If the new value is higher than the original, the result is positive a percentage increase. If the new value is lower, the result is negative a percentage decrease.
One thing to be aware of: a 50% increase followed by a 50% decrease does not bring you back to your starting point. If something increases from 100 to 150 (a 50% increase) and then decreases by 50% from 150, it lands at 75 not 100. This is because the second percentage is calculated from the new, higher value. It is a common source of confusion in financial and statistical contexts, and it is worth keeping in mind when interpreting percentage changes over time.
These are some percentages that come up frequently, expressed as decimals and fractions for quick mental math:
| Percentage | Decimal | Fraction | Quick Method |
|---|---|---|---|
| 1% | 0.01 | 1/100 | Divide by 100 |
| 5% | 0.05 | 1/20 | Divide by 20 |
| 10% | 0.10 | 1/10 | Divide by 10 |
| 20% | 0.20 | 1/5 | Divide by 5 |
| 25% | 0.25 | 1/4 | Divide by 4 |
| 33.3% | 0.333 | 1/3 | Divide by 3 |
| 50% | 0.50 | 1/2 | Divide by 2 |
| 75% | 0.75 | 3/4 | Divide by 4, multiply by 3 |
It depends on what you are calculating. To find X% of a number, use (X ÷ 100) × Number. To find what percentage X is of Y, use (X ÷ Y) × 100. To find percentage change, use ((New − Original) ÷ Original) × 100.
Subtract the original value from the new value, divide that difference by the original value, and multiply by 100. If the answer is positive, it is an increase. If it is negative, it is a decrease.
These are not the same thing. If an interest rate rises from 4% to 6%, it has increased by 2 percentage points, but it has increased by 50% relative to its original value. Percentage points describe an absolute difference between two percentages. Percentage change describes a relative difference. This distinction matters in finance, statistics, and reporting.
Yes. Convert both percentages to decimals and multiply them. For example, 20% of 15% is 0.20 × 0.15 = 0.03, which is 3%. This comes up in tax-on-tax calculations and layered discount scenarios.
It means the value decreased. A result of −15% means the new value is 15% lower than the original. The formula is the same, and the sign of the result tells you the direction.
Divide the final value by (1 + the percentage as a decimal) for an increase, or by (1 − the percentage as a decimal) for a decrease. For example, if a price is $130 after a 30% increase, the original price was 130 ÷ 1.30 = $100. This is useful for working out pre-tax or pre-discount prices.
Because each percentage is calculated from a different base. A 25% increase from 100 gives you 125. A 25% decrease from 125 gives you 93.75, not 100. The base changes each time, which is why percentage changes are not simply additive or reversible.