Percentage calculator
Work out ratios, change rates and part-of-whole percentages.
1. What percent of the whole
2. N% of a number
3. Percent change (old → new)
Percentages are simple until you have to decide which number goes on the bottom. Is a jump from 40 to 50 a rise of 20 percent or 25 percent? The formula you pick decides the answer.
This page keeps the three most common cases side by side so you can pick the right one. Results update as you type — there is no button to press.
How it works
1. What percent of the whole
Enter a part and a whole to get the part's share.
part ÷ whole × 100
30 out of 250 is 12%. Use this for pass rates, market share, or any "x out of y" question.
2. N% of a number
Enter an amount and a percentage to get the portion.
amount × percent ÷ 100
15% of 48,000 is 7,200. This is the one for tips, commission, and interest on a flat figure.
3. Percent change (old to new)
Enter the earlier value first, then the later one.
(new − old) ÷ old × 100
The result carries a sign: + for an increase, − for a decrease. Going from 40 to 50 is +25%, because the change is measured against the old value, not the new one.
Points worth knowing
- The old value is always the denominator in a change calculation. Reversing the two fields gives a different number — 50 down to 40 is −20%, not −25%.
- A drop and the rise that undoes it are never the same percentage.
- Results are rounded to two decimal places.
- A whole of zero and an old value of zero both leave the result blank, since neither can be divided by.
Terms explained
- Part
- The smaller figure whose share of the whole you want to express.
- Whole
- The total the part is measured against. It becomes the denominator.
- Percent change
- How much a value moved relative to its starting value, expressed as a signed percentage.
- Old value
- The earlier figure in a change calculation, and always the denominator.
- Percentage point
- The plain difference between two percentages. A move from 4% to 6% is 2 percentage points, but a 50% increase.
Frequently asked questions
How do I calculate what percentage one number is of another?
Divide the part by the whole and multiply by 100. Use the first panel: enter the part on the left and the total on the right. For example, 30 out of 250 gives 12%.
How do I work out percent increase or decrease?
Subtract the old value from the new one, divide by the old value, then multiply by 100. Use the third panel and enter the earlier figure first, since the old value is always the denominator.
Why does a 20% drop not cancel out a 20% rise?
Each percentage is measured against a different base. A 20% drop from 100 leaves 80, and a 20% rise from 80 only returns 96. Recovering a drop always needs a larger percentage than the drop itself.
What is the difference between percent and percentage points?
A percentage point is the plain arithmetic gap between two percentages. Moving from 4% to 6% is a rise of 2 percentage points, but a 50% increase in relative terms. News reports often mix the two.
Do I need to press a button to see the result?
No. All three panels recalculate as you type, and each result appears next to the equals sign. Figures are rounded to two decimal places.
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