How to calculate percentage increase
Percentage increase measures how much a value has grown relative to its starting point: increase % = (new − old) ÷ old × 100. Going from 80 to 100 is (100 − 80) ÷ 80 × 100 = 25%. If the result is negative, the value actually decreased.
The old value is always the denominator, and that choice is what gives the percentage its meaning: a rise of 20 is enormous on a base of 80 but negligible on a base of 8,000. If the starting value is zero, no percentage increase can be calculated at all, since dividing by zero is undefined. If you only need a fixed share of a number rather than a rise, the percentage calculator is quicker.
How to use this calculator
Enter the original value and the new value. The result is the percentage change and the absolute difference. It works for prices, salaries, populations, scores — anything that changes from one figure to another.
Entering the two values the wrong way round is the usual error and produces a different figure, not just a sign flip. Check that the field labelled original really holds the earlier number, and that both entries share the same units and basis.
Increase vs. of a number
Don't confuse "25% increase" with "25% of" a number. A 25% increase on 80 adds 20 (to reach 100); 25% of 80 is just 20. For a general up-or-down change, see the percentage change calculator; over a year, the year-over-year growth calculator.
Watch out too for percentage points. An interest rate moving from 4% to 5% is a rise of one percentage point but a 25% increase.
Frequently asked questions
- How do I calculate percentage increase?
- Subtract the old value from the new value, divide by the old value, then multiply by 100. From 80 to 100 is 25%.
- What is the percentage increase from 80 to 100?
- 25%. The difference is 20, and 20 ÷ 80 × 100 = 25%.
- What if the new value is smaller?
- You'll get a negative percentage, which means a decrease rather than an increase.
- Is a 25% increase the same as 25% of the number?
- No. A 25% increase on 80 adds 20 to make 100; 25% of 80 is simply 20.
- Does a 25% rise followed by a 25% fall return me to the start?
- No. The two percentages apply to different bases: 80 rises to 100, then a 25% fall on 100 removes 25 and leaves 75. Reversing a rise of 25% needs a fall of 20%.