Find a portion of a total
Use the first mode when you know a rate and a total, such as finding 15% of 200. Enter the percentage as 15, not 0.15, because the tool divides the rate by 100 as part of the calculation.
Percentage calculator
Find percentages, percentage shares, and percentage changes.
- ✓ Calculate a percentage portion
- ✓ Express a part as a share
- ✓ Compare old and new values
Processed on your device
See the percentage and the calculation behind it
Calculate a portion of a total, express one number as a percentage of another, or compare an old value with a new one.
Describe a change clearly
Use percentage change to compare a starting value with a later value. Keep the old and new values in their labeled fields. Reversing those fields changes the base and can produce a different percentage even when the absolute difference is the same.
Get the best result
Percentage change uses the old value as its base. A zero base cannot be used for percentage shares or changes.
A practical example
Starting point
Old value: 80. New value: 100.
Expected result
A 25% increase.
The difference is 20, and 20 ÷ 80 × 100 = 25. The old value, rather than the new value, is the base.
Troubleshooting and useful checks
The result is different from an expected percentage
Check the selected mode. Finding A% of B, finding A as a share of B, and measuring a change from A to B are three different calculations.
A zero value is rejected
A share cannot use a zero total, and percentage change cannot use a zero old value. Those formulas would divide by zero; use an absolute difference instead when no meaningful base exists.
Frequently asked questions
A little clarity before you get started.
How is percentage change calculated?
The formula is (new − old) ÷ old × 100. For example, 80 to 100 is a 25% increase.
Should I type 15 or 0.15 for fifteen percent?
Type 15 in the percentage field. The percentage-portion mode divides by 100, so entering 0.15 would calculate fifteen hundredths of one percent.
Why is an increase followed by the same decrease not neutral?
The second change uses a different base. Increasing 100 by 20% gives 120, then decreasing 120 by 20% gives 96. Equal percentage rates do not imply equal absolute amounts.
Can the result be above 100%?
Yes. A part can exceed the comparison total, and an increase can be more than the old value. Whether that result is meaningful depends on the quantities you entered.
What does a negative percentage change mean?
For a positive old value, a negative result means the new value is lower. Negative starting values can make percentage-change interpretation unintuitive, so explain the underlying values as well as the percentage.
Do I need an account to use this tool?
No. This tool is free to use without signing in. An account lets you keep a list of favorite tools.
Can I use this on a phone?
Yes, with a current browser. File support, download behavior, and available memory vary by device. For large documents and images, a computer is often more comfortable.