Percentage calculator
Work out a percentage of a number, what percent one number is of another, or how much something has increased or decreased, in percent.
Fill in the fields and press Calculate to see your result here.
How this calculation works
Each mode uses one of three everyday percentage formulas: a percentage of a number is (percentage ÷ 100) × number; finding what percent one number is of another is (part ÷ whole) × 100; and percentage change between two values is ((new − old) ÷ old) × 100, which comes out negative for a decrease.
Tips
Negative means a decrease
In the % change tab, a negative result simply means the value went down rather than up — the size of the number is the percentage of change either way.
Watch the denominator
“X is what % of Y” divides by Y, not X. Swapping the two fields by mistake is the most common source of a wrong answer.
Percent changes aren't symmetrical
Taking 20% off and then adding 20% back doesn't return you to the start: 100 becomes 80, and 20% of 80 is only 16, so you end at 96. The base changes after every step.
Percentage points are not percent
A rate that moves from 4% to 6% has risen by 2 percentage points, but that is a 50% increase. Use the % change tab when you want the relative change.
A quick mental shortcut
10% of a number is the number with the decimal point moved one place to the left. Half of that is 5%, and 10% plus 5% gives you 15%, which is handy for tips and discounts.
Frequently asked questions
Can I calculate a percentage decrease?
Yes. Use the % change tab and enter the earlier value as “From” and the later value as “To”. A drop shows up as a negative percentage.
Why do I get an error with 0 in the From field?
Percentage change divides by the starting value, so a starting value of 0 has no defined percentage change.
Does this round the result?
Results are shown to two decimal places for readability, but the calculation itself uses the full precision of your inputs.