What This Calculator Does

The Increase/Decrease Calculator applies percentage changes to starting values, giving you the final result after increasing or decreasing by a percentage. This calculator handles both operations in one interface, making it perfect for salary raises, price adjustments, tax calculations, and budget changes.

Increase formula: Result = Base × (1 + Percentage/100)

Decrease formula: Result = Base × (1 − Percentage/100)

Both formulas show the percentage amount and the final result, giving you complete transparency into how the calculation works. For a detailed explanation of these formulas and when to use them, read our guide Increase and Decrease Percentage Formula Explained.

How the Formulas Work

Understanding why these formulas work helps you apply them confidently in any scenario. Both formulas use a multiplication approach that's faster and more accurate than calculating the percentage amount separately.

Increase Formula: Base × (1 + Percentage/100)

When you multiply by (1 + rate), you keep the original value (the "1") and add the increase (the rate). This combines two steps into one efficient calculation.

Example: Increase $200 by 15%

Convert percentage to decimal: 15 ÷ 100 = 0.15
Add 1 to the decimal: 1 + 0.15 = 1.15
Multiply base by the result: $200 × 1.15 = $230
Result: $230

Decrease Formula: Base × (1 − Percentage/100)

When you multiply by (1 - rate), you keep the original value (the "1") and subtract the decrease (the rate). This efficiently calculates what remains after the reduction.

Example: Decrease 500 by 20%

Convert percentage to decimal: 20 ÷ 100 = 0.20
Subtract from 1: 1 − 0.20 = 0.80
Multiply base by the result: 500 × 0.80 = 400
Result: 400

For comprehensive coverage of percentage increase and decrease calculations with additional examples, see How to Calculate Percentage Increase and Decrease.

Real-World Use Cases

Percentage increases and decreases appear constantly in business, shopping, education, and personal finance. Here are practical examples showing how these calculations apply to everyday scenarios:

Salary raises: "Your $60,000 salary increased by 5%"
$60,000 × (1 + 5/100) = $60,000 × 1.05 = $63,000
Your new salary is $63,000.

Sales tax: "Add 7.5% tax to $150 subtotal"
$150 × (1 + 7.5/100) = $150 × 1.075 = $161.25
Your total with tax is $161.25.

Price cuts: "Item reduced by 30% from $80"
$80 × (1 − 30/100) = $80 × 0.70 = $56
The sale price is $56.

Budget reductions: "Cut department budget by 12% from $25,000"
$25,000 × (1 − 12/100) = $25,000 × 0.88 = $22,000
The new budget is $22,000.

For more practical shopping math examples and strategies, check out Shopping Math: Discounts and Sales Tax.

Excel and Spreadsheet Formulas

Both increase and decrease formulas translate directly into Excel or Google Sheets, allowing you to automate percentage calculations across datasets.

Increase formula in Excel:
=Base*(1+Percentage/100) or =Base*(1+Percentage%)
Example: Increase $200 by 15% → =200*(1+15/100) or =200*1.15 → Result: 230

Decrease formula in Excel:
=Base*(1-Percentage/100) or =Base*(1-Percentage%)
Example: Decrease 500 by 20% → =500*(1-20/100) or =500*0.8 → Result: 400

Using cell references for repeatable calculations:
If base is in cell A1 and percentage is in cell B1:

Increase: =A1*(1+B1/100)
Decrease: =A1*(1-B1/100)

This pattern works for any row, making it easy to calculate percentage increases or decreases across large datasets.