What is a Percentage Calculator?
The percentage calculator computes proportions, increase/decrease rates, and discounted prices — answering questions like 'What percent of B is A?' or 'What is the result of a percent change?'
How it's calculated
Percentage = part ÷ whole × 100
Percent change = (new value − old value) ÷ old value × 100
The denominator for percent change is always the original value.
Percent vs. percentage point
If approval rating rises from 40% to 44%, that is a 4 percentage point (pp) increase and also a 10% increase. Both are correct, but they describe very different magnitudes. That is why financial and statistical reporting always distinguishes 'pp' from '%'.
Good to know
- A 50% increase followed by a 50% decrease does not return to the original. 100 → 150 → 75. This is why a stock that drops 50% needs a 100% gain to fully recover.
- The percent sign (%) evolved from a handwritten abbreviation of the Italian per cento (per hundred).
- Per mille (‰) is parts-per-thousand, used for things like blood alcohol concentration or ocean salinity.
- Stacked discounts do not simply add. A 30% discount followed by an additional 20% is not 50% off — it is actually 44% off (100 → 70 → 56).
- The same trap applies to sales tax: subtracting a flat percentage from a tax-included total gives the wrong number — you have to divide, not subtract.
Frequently asked questions
Q. What is the total discount for 30% off followed by an additional 20% off?
44%. The math is 100 × 0.7 × 0.8 = 56, so you pay 56% of the original price.
Q. How many times larger is a 100% increase?
Double. A 200% increase means 3 times the original, and 300% means 4 times.
Q. When should I use % versus percentage points (pp)?
Use pp for the difference between two percentages, and % for the relative change from an original value.