Everyday maths
How to Calculate Percentage Increase
A simple guide to percentage increase, from bills and prices to business metrics, with the baseline mistake explained clearly.
Percentage increase compares how much a value has risen relative to where it started. Use the percentage increase calculator when you want to check the change between an old value and a new value.
The short version
The percentage increase formula is:
Percentage increase = (new value - old value) / old value x 100
If a price rises from 80 to 100, the increase is 20. Divide 20 by the old value of 80, then multiply by 100. The percentage increase is 25%.
Try it with your own numbers
Use the percentage increase calculator for old-to-new comparisons. Use the percentage calculator for general percentage questions.
How the calculation works
The old value is the baseline. The difference between the new and old value is the change. Dividing by the old value tells you how large the change is compared with the starting point.
This is why a rise from 10 to 20 is a 100% increase, while a rise from 100 to 110 is only a 10% increase. Both changes can feel important, but the baseline is different.
A worked example
Suppose a monthly bill increases from 64 to 72.
- Change: 72 - 64 = 8
- Divide by old value: 8 / 64 = 0.125
- Convert to percent: 0.125 x 100 = 12.5%
The bill increased by 12.5%.
Watch-outs
- Dividing by the new value instead of the old value.
- Confusing percentage points with percent change.
- Using the same formula for a decrease without changing wording.
- Forgetting that a 50% decrease needs a 100% increase to return to the original value.
How to read the result
Use percentage increase to compare price rises, income changes, growth rates, bill changes, traffic increases, and business metrics. For longer-term growth, use a compound measure such as CAGR instead of a simple one-period percentage.
Tools mentioned in this article
Reader questions
What if the old value is zero?
Percentage increase from zero is not defined because the formula divides by the old value.
Is percentage increase the same as percentage points?
No. Moving from 5% to 7% is a 2 percentage point rise, but a 40% relative increase.
Can the result be negative?
If the new value is lower than the old value, the same calculation gives a negative percentage change.
Why does the baseline matter?
The baseline tells you what the change is being compared with. A 10-unit change can be huge or tiny depending on the starting value.
