How to Calculate Percentage Change
Percentage change measures how much a value has increased or decreased relative to where it started. It is useful for prices, revenue, traffic, conversion rates, costs, salaries, investment values, and many other comparisons. This guide explains the formula, worked examples, reverse calculations, and the mistakes that commonly produce misleading results.
Last reviewed: 2026-09-13
Percentage change formula
Subtract the original value from the new value, divide that difference by the original value, and multiply by 100.
- Percentage Change = ((New Value − Original Value) ÷ Original Value) × 100
A positive result means the value increased. A negative result means it decreased. You can run either calculation with the Percentage Calculator.
Percentage increase example
Suppose monthly revenue rises from $80,000 to $100,000. The absolute increase is $20,000, but percentage change shows the increase relative to the original revenue.
- Increase = $100,000 − $80,000 = $20,000
- Percentage Increase = ($20,000 ÷ $80,000) × 100
- Percentage Increase = 25%
Monthly revenue increased by 25%.
Percentage decrease example
Suppose a monthly software cost falls from $2,500 to $2,000.
- Decrease = $2,500 − $2,000 = $500
- Percentage Decrease = ($500 ÷ $2,500) × 100
- Percentage Decrease = 20%
The cost decreased by 20%.
Why the original value is the denominator
Percentage change answers how large the change was compared with the starting point. That is why the original value belongs in the denominator. Dividing by the new value answers a different question and produces a different percentage.
For example, a move from 80 to 100 is a 20-unit increase. Relative to the original 80, that change is 25%. Dividing 20 by the new value of 100 would produce 20%, which does not represent the percentage increase from the starting value.
Percentage increase and decrease are not symmetrical
A percentage increase followed by the same percentage decrease does not normally return a value to its starting point because the second percentage is applied to a different base.
- 80 increased by 25% = 100
- 100 decreased by 25% = 75
To return from 100 to 80, the required decrease is 20%. This same base-value effect matters when analyzing prices, portfolio movements, discounts, and business metrics.
How to find the new value after a percentage change
If you know the original value and the percentage change, you can calculate the new value directly.
- After an increase: New Value = Original Value × (1 + Rate)
- After a decrease: New Value = Original Value × (1 − Rate)
For a $500 price increased by 12%, convert 12% to 0.12 and calculate $500 × 1.12 = $560. For a $500 price reduced by 12%, calculate $500 × 0.88 = $440. For sale-price calculations involving multiple offers, use the Discount Calculator or read how to calculate a discount.
How to find the original value
When the final value and percentage change are known, reverse the multiplier instead of simply subtracting the percentage from the final number.
- Before an increase: Original Value = New Value ÷ (1 + Rate)
- Before a decrease: Original Value = New Value ÷ (1 − Rate)
If a value is $120 after a 20% increase, the original value is $120 ÷ 1.20 = $100.
Percentage change vs percentage points
Percentage change and percentage-point change are different. If a conversion rate rises from 4% to 5%, it increased by 1 percentage point, but the relative percentage increase is 25% because (5 − 4) ÷ 4 × 100 = 25%.
This distinction is especially important when reporting rates, margins, interest rates, and survey results. For campaign performance, calculate the underlying rate first with the Conversion Rate Calculator.
Using percentage change in business
Percentage change makes differently sized periods or categories easier to compare. A $10,000 revenue increase is much more significant for a business starting at $20,000 than for one starting at $1 million. The relative percentage provides that context.
However, percentage change should not replace the underlying business metric. A revenue increase does not automatically mean profit improved. Pair growth analysis with the Profit Margin Calculator when costs are relevant.
Common percentage-change mistakes
- Using the new value as the denominator. Standard percentage change uses the original value.
- Confusing percentage points with percent change. A rate moving from 10% to 12% rises 2 percentage points but 20% in relative terms.
- Adding sequential percentage changes. Successive changes compound because each one applies to a new base.
- Ignoring a zero starting value. Standard percentage change is undefined when the original value is zero.
- Comparing mismatched periods. Make sure both values represent comparable definitions, time windows, currencies, and scopes.
- Rounding too early. Keep extra decimal places during the calculation and round the final result.
Quick percentage-change checklist
Identify the true starting value, confirm that both values are comparable, calculate the difference, divide by the starting value, and convert the result to a percentage. Then label the result clearly as an increase or decrease and retain the absolute values so readers can see the scale behind the percentage.