Percentage Change
Increase or decrease of a value as a percentage.
Formula
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Example
From 50 to 60 = +20%
How it works
Percentage change compares how much a value has gone up or down relative to where it started. First find the difference between the new and old values, then divide by the original value to measure the change as a fraction of the starting amount, and multiply by 100 to convert that fraction into a percent. A positive result means an increase, while a negative result means a decrease.
When to use it
Use this when comparing prices, scores, measurements, or any quantity that changes over time. It is especially helpful when you want to know how big a change is relative to the original amount, not just the raw difference.
Worked example, step by step
Original value (old) = 80 New value (new) = 68 Step 1: Find the change = 68 - 80 = -12 Step 2: Divide by the original value = -12 / 80 = -0.15 Step 3: Convert to a percentage = -0.15 × 100 = -15% Final answer: the percentage change is -15%, so this is a 15% decrease.
Common mistakes to avoid
- Dividing by the new value instead of the original value
- Forgetting to keep the negative sign for a decrease
- Using the formula for absolute change instead of percentage change
Did You Know?
A 50% drop followed by a 50% rise does NOT return you to the start — you end up 25% below, a trap that fools many investors.
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