Percentage Change Formula: How to Calculate Increase and Decrease
Learn the simple formula to calculate percentage growth or decline for sales, grades, or statistics.
Calculating percentage change is one of the most useful math skills for everyday life. Whether you're tracking stock prices, analyzing sales data, or just checking if a sale is actually a good deal, this formula is essential.
The Formula
The formula for percentage change is:
$$ Percentage \ Change = \frac{New \ Value - Old \ Value}{Old \ Value} \times 100 $$
Positive vs. Negative
- Positive Result (+): Percentage Increase
- Negative Result (-): Percentage Decrease
Example 1: Percentage Increase
Last year, a coffee shop sold 500 cups a day. This year, they sell 600. What is the growth?
- New Value = 600
- Old Value = 500
$$ \frac{600 - 500}{500} \times 100 = \frac{100}{500} \times 100 = 0.2 \times 100 = 20% $$
Result: 20% Increase.
Example 2: Percentage Decrease
A shirt was $50, and now it's on sale for $35. What is the discount?
- New Value = 35
- Old Value = 50
$$ \frac{35 - 50}{50} \times 100 = \frac{-15}{50} \times 100 = -0.3 \times 100 = -30% $$
Result: 30% Decrease (or 30% Off).
Fast Calculation: Don't want to do the math? Use our Percentage Calculator for instant answers.