Experimental data & uncertainty · SL/HL
Percentage change & difference
Calculate a percentage change or percentage difference.
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Number formats & units
Use decimal dots in datasets. Single values also accept decimal commas and scientific notation such as 1.2e-3 or 1.2 × 10⁻³.
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Result & working
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Interpretation & assumptions
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Formula & example
The relationship
What the variables mean
| Symbol | Meaning |
|---|---|
| change | Directional change relative to an initial value. |
| difference | Symmetric comparison when neither value is the accepted baseline. |
Worked example
- Calculation
- Percentage change
- New value / value A
- 125
- Initial value / value B
- 100
25%
Follow the example steps
- percentage change = (new − initial)/|initial| × 100
- = (125 − (100))/|100| × 100 = 25%
Common mistakes
Divide by the initial value for percentage change.
Incorrect approach
50 → 60: change = 100 × 10/60 ≈ 16.7%
Correct approach
change = 100 × (60 − 50)/50 = 20%
More checks before you submit
- Percentage change is undefined when the initial value is zero.
Method notes
Read the wording carefully: “change” and “difference” have different denominators.