How to use the percentage calculator
- Pick the question you’re answering with the three tabs.
- Type your two numbers — the answer and the worked formula appear instantly.
- Switch tabs any time; your figures stay put.
The three percentage formulas
1. What is X% of Y?
Use this for discounts, tips and tax. Example: 20% of 150 = (20 ÷ 100) × 150 = 30.
2. X is what percent of Y?
Use this for scores and shares of a total. Example: 30 out of 150 = (30 ÷ 150) × 100 = 20%.
3. Percentage increase or decrease
Use this for price changes and growth. A rise from 80 to 100 = ((100 − 80) ÷ 80) × 100 = +25%. A negative result means a decrease.
Worked examples
A 15% tip on a $46 bill
15% of 46 = (15 ÷ 100) × 46 = $6.90. Total to pay: $52.90.
You scored 38 out of 50
(38 ÷ 50) × 100 = 76%.
Rent went from $1,200 to $1,320
((1320 − 1200) ÷ 1200) × 100 = +10% increase.
Where percentages come up every day
Percentages are one of the most useful pieces of everyday maths, which is why this is such a commonly searched calculator. You’ll reach for one of the three modes above whenever you deal with:
- Shopping: working out a “30% off” sale price, or checking how much a discount actually saves you.
- Tips and service charges: adding 10%, 15% or 20% to a restaurant bill.
- Tax: adding sales tax or VAT, or stripping it back out of a tax-inclusive price.
- Test scores and grades: turning “38 out of 50” into a percentage.
- Finance: interest rates, investment returns and how much a price has risen or fallen.
- Statistics and news: making sense of “up 12%” or “a 3 percentage-point increase”.
Percentages, fractions and decimals
A percentage is just a fraction out of 100, so it can always be written three ways. Recognising the common ones makes mental maths much faster:
| Percentage | Fraction | Decimal |
|---|---|---|
| 10% | 1/10 | 0.10 |
| 20% | 1/5 | 0.20 |
| 25% | 1/4 | 0.25 |
| 50% | 1/2 | 0.50 |
| 75% | 3/4 | 0.75 |
| 100% | 1 | 1.00 |
To turn a percentage into a decimal, divide by 100 (move the point two places left). To go back, multiply by 100. That single idea is behind all three formulas above.
Frequently asked questions
Use the first tab to find the percentage of the price, then subtract it. For 25% off a $80 item: 25% of 80 is $20, so you pay $60.
If a rate moves from 5% to 6%, that is a 1 percentage-point rise but a 20% increase. Percentage points compare the percentages directly; percentage change compares them relative to the starting value.
If a price already includes, say, 20% tax, divide by 1.20 to get the pre-tax amount. A $120 total ÷ 1.20 = $100 before tax.
A negative result means the value went down. For example from 100 to 75 is a −25% change, i.e. a 25% decrease.
Find 10% first by moving the decimal point one place left, then scale. 10% of 240 is 24, so 20% is 48 and 5% is 12. A handy trick: X% of Y equals Y% of X, so 8% of 50 is the same as 50% of 8 — which is just 4.
Percentage difference compares two values without treating either as the “original”: take the difference, divide by the average of the two, and multiply by 100. It differs from percentage change, which always divides by the starting value.