Percentage
How to use the percentage calculator
Choose an operation, enter a value and percentage, and the result updates immediately. Use “percent of” for tips and discounts, increase or decrease for price changes, and the reverse option when you know the result but need the original amount.
Formula and method
Percent of a value = value × percentage ÷ 100. Percentage change = (new value − original value) ÷ original value × 100.
Worked example
For a 15% tip on $80, calculate 80 × 15 ÷ 100 = $12. The total bill is $92.
How to interpret the result
Read the result in the context of the selected operation. “Percent of” returns a portion of the starting value, while increase and decrease return a changed total. Percentage change compares two values and uses the original value as its denominator. That base matters: a 20% fall followed by a 20% rise does not return to the starting point.
Important limitations
- Negative percentages are supported.
- A reverse percentage cannot be calculated when the percentage is zero.
Common questions
What is the difference between percent and percentage points?
Percent describes a relative change. Percentage points describe the direct difference between two percentages. Moving from 20% to 25% is a rise of 5 percentage points, or a 25% relative increase.
Why can reverse-percentage answers look larger than expected?
The known result is divided by the remaining or increased share of the original. A price after a 20% discount is 80% of the original, so the reverse calculation divides by 0.80 rather than adding 20%.
Related tools
Method and examples reviewed September 8, 2026.