Your result
What your result means
Going from 80 to 92 is an increase of 15% ((92 − 80) ÷ 80 × 100).
The math
Formula and sources
A% of B = A ÷ 100 × B A as % of B = A ÷ B × 100 % change A → B = (B − A) ÷ |A| × 100
- A
- first value (the percent, the part, or the starting value)
- B
- second value (the base, the whole, or the new value)
How to calculate a percentage increase between two numbers: subtract the starting value from the new value, divide by the absolute value of the starting value, then multiply by 100. Example: 80 → 92 is (92 − 80) ÷ 80 × 100 = 15% increase. A fall from 92 → 80 is −13.04%, not −15%, because percent change is always measured against the starting value. Percent change from zero is undefined — describe that change in absolute terms instead.
Sources we checked this against
- 1Calculating percent changesU.S. Bureau of Labor Statistics · bls.gov
- 2How to use the Consumer Price Index for escalationU.S. Bureau of Labor Statistics · bls.gov
Formula last checked 2026-11-05. Found an error? Tell us and we will fix it.
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Step by step
Two worked examples
BLS: 12-month CPI change
Answer
6.4544%
- What do you want to find?
- Percent change from A to B
- A
- 278.802
- B
- 296.797
The BLS shows CPI-U rising from 278.802 (Dec 2021) to 296.797 (Dec 2022): 17.995 ÷ 278.802 × 100 = 6.4544%, published as 6.5%.
Sales tax on a purchase
Answer
46.4
- What do you want to find?
- What is A% of B?
- A
- 7.25
- B
- 640
7.25% of $640: 7.25 ÷ 100 × 640 = 46.4.
| Result | Example 1 | Example 2 |
|---|---|---|
| Answer | 6.4544% | 46.4 |
Questions
Frequently asked questions
What is the difference between percent and percentage points?
If a rate goes from 4% to 5%, it rose 1 percentage point, but 25 percent (1 ÷ 4). News reports on interest rates usually mean percentage points.
How do I reverse a percent increase?
Divide by (1 + the increase). A price that rose 20% to $60 was $60 ÷ 1.2 = $50 before — not $60 minus 20%.
Why can’t I calculate a percent change from zero?
Percent change divides by the starting value, and division by zero is undefined. Describe the change in absolute terms instead.
How do I calculate a percentage of money?
Multiply the amount by the percent, then divide by 100. 15% of $80 is $80 × 15 ÷ 100 = $12. Moving the decimal also works: 15% is 0.15, and 0.15 × $80 = $12. Use the “A% of B” mode above for tips, tax, discounts and portfolio weights.
How do I calculate percentage off a price?
Multiply the original price by (1 − the discount). 25% off $80 is $80 × 0.75 = $60, so you save $20. Two discounts stack by multiplying, not adding: 20% off and then another 10% off is 28% off in total, not 30%.