Percentage increase or decrease
Calculate the percentage increase / decrease
What this calculator does
You enter a starting value (“From”) and an ending value (“To”). The result is the relative change from start to finish, as a percentage of the start. A positive answer means an increase; a negative answer means a decrease.
Use it for sale prices vs list price, month-over-month metrics, salary adjustments, or any “before and after” where the first number is the meaningful baseline.
Formula
((new value − old value) ÷ old value) × 100 = percent change
The old value is always the denominator: you are asking how big the difference is compared to where you started. If the old value is 0, percent change is undefined (division by zero).
Worked example
From 16 to 25: (25 − 16) ÷ 16 = 9 ÷ 16 = 0.5625; 0.5625 × 100 = 56.25% increase.
Common mistakes
- Wrong baseline. Dividing by the new value instead of the old one answers a different question and skews the %.
- Percent change vs percentage points. Moving from 3% to 4% is a one percentage point rise, but roughly a 33% relative increase in the rate itself. This tool reports relative % change, not points.
Common questions
- How do you calculate percentage increase or decrease?
Compute ((new − old) ÷ old) × 100. Positive means up from the start; negative means down.
- What number do you divide by?
Always the original (“From”) value—the baseline you are measuring change from.
- Why is percent change undefined when the old value is zero?
The formula divides by the old value. Division by zero is undefined, so there is no meaningful percent change from a starting point of zero.
- Percent change vs percentage points—what is the difference?
Points add or subtract on the percent scale (3% → 4% is +1 point). Relative % change compares the gap to the starting rate (that same move is about +33% relative to 3%). This calculator does relative change.
- What is the percent increase from 100 to 120?
20%. (120 − 100) ÷ 100 = 0.2; × 100 = 20%.
- Is a decrease just a negative percent change?
Yes. If the new value is smaller than the old one, the formula returns a negative percentage.