How do I calculate a percentage of an amount?
Divide the percentage by 100 and multiply by the amount. For example, 15 ÷ 100 × 200 = 30.
Percentage Calculator
Work out percentages for everyday comparisons, discounts, and price changes. Choose an operation, enter two values, and calculate a percentage or an adjusted amount. Results use the same units as your inputs; no currency conversion or tax rules are applied.
Calculate a percentage
How it works
Percent means per hundred. To find a percentage of an amount, divide the percentage by 100 and multiply by the amount. To express a part as a percentage, divide the part by the whole and multiply by 100. Percentage change compares the difference with the original value. Increasing or decreasing an amount applies a multiplier of 1 plus or minus the percentage divided by 100.
Worked example
15% of 200 is 30. If a price of 200 is discounted by 15%, the new price is 170. A change from 200 to 250 is a 25% increase. In contrast, changing from 250 back to 200 is a 20% decrease, because the original value is different.
Formulas
Percentage of an amount = percentage ÷ 100 × amount; Part as a percentage = part ÷ whole × 100; Percentage change = (new − original) ÷ original × 100; Increased amount = original × (1 + percentage ÷ 100); Decreased amount = original × (1 − percentage ÷ 100)
Not financial advice
General arithmetic only, not financial, tax, investment, or legal advice. Verify important calculations independently. Results do not include fees, interest compounding, currency conversion, or jurisdiction-specific tax rules. Use positive starting values for ordinary price comparisons; signed inputs follow the displayed algebraic formulas.
Frequently asked questions
How do I calculate a discount?
Choose Decrease by a percentage, enter the original amount and discount rate, then calculate. A 15% discount on 200 gives 170, a saving of 30.
What is the difference between percentage change and percentage points?
A change from 20% to 25% is an increase of 5 percentage points, but a relative percentage increase of 25%. This calculator's Percentage change mode measures relative change.
Can I calculate percentage change from zero?
No. The formula divides by the original value, so percentage change from zero is undefined. The calculator reports an error instead of returning infinity.
Are values rounded?
The arithmetic uses JavaScript number precision. Displayed values are rounded for readability, not for a particular currency's accounting rules.
Can I use negative numbers?
Yes. Signed inputs follow the displayed formulas. For usual prices and discounts, use positive amounts. A decrease greater than 100% can produce a negative amount; the result is arithmetic, not a valid-price guarantee.