Learn how to add percentages correctly and see why 20% plus 10% is not the same as a simple 30% change.
Why 20% + 10% Isn’t 30%
When you apply a 20% increase followed by a 10% increase, the second increase is calculated on the new value, not the original one. Starting at 100, a 20% increase gives 120. A further 10% increase on 120 gives 132. The overall change from 100 to 132 is 32%, not 30%.How to Add Percentages Correctly
To combine two percentage changes, turn each change into a factor. For example, +20% becomes 1.20, and +10% becomes 1.10. Multiply the factors (1.20 × 1.10 = 1.32) and then convert the combined factor back into a percentage change by subtracting 1 and multiplying by 100.Common Mistakes with Adding Percentages
A very common mistake is simply adding percentage figures together without accounting for compounding, especially with discounts, interest, and year‑on‑year price changes. Another mistake is forgetting that a 20% increase followed by a 20% decrease does not bring you back to the starting point; it leaves you below where you started.Adding Percentages Calculator
Enter a starting value and two percentage changes to see the final value and the true overall percentage change.
Calculation Result
Starting value: 0
After first change: 0
After second change: 0
Overall percentage change: 0%
Formula Used
First change factor = 1 + (First % ÷ 100)
Second change factor = 1 + (Second % ÷ 100)
Combined factor = First factor × Second factor
Overall percentage change = (Combined factor − 1) × 100
