Percentage Increase & Decrease Calculator
Calculate the final value after a percentage increase or decrease, including negative values and edge cases.
Calculate the final value after applying a percentage increase or decrease to an initial number.
Percentage Increase and Decrease Guide
Percentage increase and decrease describe how a value changes when a percentage is added or subtracted from the original amount.
These calculations appear in many real-world situations such as price changes, discounts, salary adjustments, investment returns, and population growth.
Understanding how to apply percentage changes correctly helps you measure how quantities grow or shrink relative to their starting value.
Where Percentage Increase and Decrease Are Used
- Retail price increases or discounts
- Salary raises or reductions
- Investment gains and losses
- Population growth or decline
- Revenue and sales performance analysis
Percentage Increase and Decrease Formula
To apply a percentage change, multiply the original value by a percentage multiplier.
Final Value = Initial Value × (1 ± p) Where:
- p is the percentage written as a decimal
- Use + for increases
- Use − for decreases
Example: 25% = 0.25 The multiplier adjusts the original value to produce the final result.
Example — Percentage Increase
A jacket costs $80. The price increases by 25%.
Step 1: Convert the percent to decimal.
25% = 0.25 Step 2: Apply the increase formula.
80 × (1 + 0.25) Step 3: Calculate the result.
80 × 1.25 = 100 Final value: $100
You can calculate percentage increases quickly using the Percentage Increase / Decrease calculator.
Example — Percentage Decrease
A phone costs $600 and is discounted by 15%.
Step 1: Convert the percent to decimal.
15% = 0.15 Step 2: Apply the decrease formula.
600 × (1 − 0.15) Step 3: Calculate the result.
600 × 0.85 = 510 Final value: $510
Edge Cases
If the starting value is zero, applying any percentage increase still produces zero.
0 × (1 + 0.50) = 0 Because the base value is zero, the result cannot change.
A percentage decrease applied to zero also remains zero.
0 × (1 − 0.30) = 0 The value remains unchanged because there is no quantity to reduce.
Suppose a price of $50 increases by 200%.
50 × (1 + 2.00) = 150 A 200% increase adds twice the original value, producing a final value of $150.
A value of $120 increases by 2.5%.
2.5% = 0.025 120 × (1 + 0.025) = 123 Small percentage adjustments like this are common in finance and interest calculations.
Curious Mind
Sometimes a value changes by several percentages in sequence. For example, a price might increase by 10% and later decrease by 5%.
When multiple percentage changes occur, each one applies to the updated value rather than the original amount.
You can explore how sequential percentage changes work using the Stacked Percentage Change calculator .
Practice Problems
- Increase 200 by 10%.
- Decrease 450 by 20%.
- Increase 120 by 5%.
- Decrease 980 by 12%.
- Increase 75 by 30%.
Formula Summary
Final Value = Initial Value × (1 + p) Final Value = Initial Value × (1 − p) Frequently Asked Questions
How do you calculate a percentage increase?
To calculate a percentage increase, multiply the original value by the multiplier (1 + p), where p is the percentage written as a decimal.
For example, increasing 80 by 25%:
80 × (1 + 0.25) = 100 How do you calculate a percentage decrease?
To calculate a percentage decrease, multiply the original value by the multiplier (1 − p).
For example, decreasing 600 by 15%:
600 × (1 − 0.15) = 510 Is percentage increase the same as percent change?
No. Percentage increase or decrease applies a percentage to a single starting value.
Percent change compares two values and measures the difference between them relative to the original value.
What happens if the percentage is applied multiple times?
When percentage changes occur more than once, they must be applied sequentially to the updated value.
This process is called stacked percentage change.
Refer to the Curious Mind section above to explore this concept further.