How it works
First divide the percentage by 100, then multiply by the original value. For an increase, add that amount to the original; for a decrease, subtract it. For example, 20% of 1,500 is 300.
Percentage amount = value × percentage / 100
Worked example
Show example inputs and result
Value: 1,500 · Percentage (%): 20 · Operation: Percentage of a value.
- Result
- 300
- Percentage amount
- 300
Questions and answers
Does adding 20% undo subtracting 20%?
No. The second percentage acts on a different base: 100 → 80 → 96. To reverse a 20% reduction you need a 25% increase.
Why are some results rounded?
Results display up to 8 decimal places. Calculations use the unrounded values; very small values use scientific notation. JavaScript floating-point arithmetic can introduce tiny rounding differences.
Are my inputs sent to a server?
The calculator processes inputs in your browser. Its code does not send your values to a server.
Method reviewed: October 8, 2026 · Methods & accuracy