Percent Increase vs Percent Decrease
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Direct answer
Both calculations use the original value as the baseline. Increase uses new − old; decrease magnitude uses old − new.
Formula and method
Increase = (new − old)/old × 100; decrease = (old − new)/old × 100
The calculation keeps full precision through the formula and rounds only the displayed answer.
Step-by-step calculation
- Confirm the original is positive.
- Compare new with old.
- Choose the direction-specific numerator.
- Keep the original in the denominator.
Worked examples
80 to 100
Increase = 20 ÷ 80 = 25%.
100 to 80
Decrease = 20 ÷ 100 = 20%.
Round trip
A 25% rise from 80 reaches 100; a 20% fall from 100 returns to 80.
Interpretation and edge cases
- Increase and decrease are not symmetric.
- A result can exceed 100% for an increase, while ordinary decrease from a nonnegative value is capped at 100%.
- Negative values need contextual interpretation.
Frequently asked questions
Can an increase exceed 100%?
Yes.
Can a decrease exceed 100%?
Not when a nonnegative quantity cannot go below zero.
Why are the reverse rates different?
They use different starting values.
Sources and transparency
The formulas and examples were evidence-checked on 2026-09-10. This is educational mathematical content. It does not replace a field-specific standard, accounting policy, laboratory method, contractual definition or professional judgment.
Use this resource
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