Percent
Per cent means hundredths. Choose what you want to calculate and see how the answer is found — so you can do it yourself next time.
The explanation is shown. Quick: percent of, what percentage, change, discount and VAT. Advanced: also several changes in a row, chain discount, index numbers and percentage points — and a percentage table.
Your numbers
Answer
20 % of 250
50
How to work it out
- 11 % = 250 / 100 = 2.5Per cent means hundredths — first find one hundredth.
- 220 % = 2.5 · 20 = 50
The formula
part = p/100 · whole
Per cent means «hundredths»: 20 % = 20/100 = 0.20.
p = part / whole · 100
change % = (after − before) / before · 100
Always divide by the number BEFORE the change.
new = old · (1 ± p/100)
The growth factor: +20 % is · 1.20, and −20 % is · 0.80.
end = start · (1 + p₁/100) · (1 + p₂/100) · …
Several changes in a row: multiply the factors — never add the percentages.
index = value / base value · 100
percentage points = p₂ − p₁
Percentage points are the difference between two percentages; per cent is the change relative to the first.
In depth: more numbers and “what if”
Percentage table for 250
| Percent | The part |
|---|---|
| 5 % | 12.5 |
| 10 % | 25 |
| 20 % | 50 |
| 25 % | 62.5 |
| 50 % | 125 |
| 75 % | 187.5 |
More: Numbers and percentages
- FractionsAdd, subtract, multiply and divide fractions — and simplify the answer.
- Powers and rootsPowers, square roots, nth roots and numbers as powers of 10.
- Primes and divisorsIs it a prime? Prime factors, divisors, GCD and LCM.
- Rounding and estimatingRound to decimals, tens or significant figures — and make an estimate.
- Order of operationsEnter a calculation and see it worked out step by step in the right order.
- Number systems and Roman numeralsBinary, hexadecimal and Roman numerals — converted both ways with working.