Easy Formula to Reduce a Number by a Percentage in Excel
Microsoft Excel allows you to reduce a number by a percentage quickly and accurately, making it a valuable skill for everyday spreadsheet tasks. This calculation is commonly used for applying discounts, calculating sale prices, adjusting budgets, and updating financial data.
In this guide, you will learn the formula to reduce a number by a percentage in Excel, along with practical examples and easy-to-read tables.
Basic Formula to Decrease a Number by a Percentage
The best formula to reduce a number by a percentage in Excel multiplies the original number by (1 minus the percentage).
Formula: =original_number * (1 - percentage)
Excel treats percentages as decimals. For example, 10% becomes 0.1.
Step-by-Step Example
Suppose you have a price of $100 in cell A1 and want to reduce it by 20% in cell B1.
- Enter the original number (100) in cell A1.
- Enter the percentage (20%) in cell B1, or type it directly.
- In cell C1, type:
=A1*(1-0.20)or=A1*(1-B1)if B1 holds 20%. - Press Enter. The result shows 80.
This works because 100 * (1 – 0.20) = 100 * 0.80 = 80.
Another option subtracts the percentage amount first:
=original_number - (original_number * percentage)
Example: =A1 - (A1 * 0.20)
Both formulas give the same result.
Applying the Formula to Multiple Numbers
When you have a list of numbers to reduce by the same percentage, use cell references and drag the formula.
Example: Calculating Sale Prices with Discount
Set up data like this:
| Item | Original Price | Discount Percentage | Reduced Price Formula | Result |
|---|---|---|---|---|
| Shirt | 50 | 15% | =B2*(1-C2) | 42.50 |
| Pants | 80 | 15% | =B3*(1-C3) | 68.00 |
| Shoes | 120 | 15% | =B4*(1-C4) | 102.00 |
Steps:
- Enter original prices in column B.
- Enter the discount percentage (15%) in column C. Format as percentage.
- In D2, type
=B2*(1-C2). - Drag the fill handle down to D4.
Excel copies the formula and adjusts references. This applies percentage reduction to the whole list.
For different percentages per row, enter them in column C.
Using Absolute References for Fixed Percentage
Keep the percentage fixed when copying formulas across many rows. Use dollar signs ($) for absolute reference.
Example: Put the percentage in cell E1 (20%).
Formula in the reduced price column: =B2*(1-$E$1)
Drag down. The reference to E1 stays fixed.
This method suits large datasets for bulk percentage decrease.
Alternative Method: Paste Special for Quick Reduction
Apply a percentage reduction without formulas using Paste Special.
- Enter the multiplier in a cell, like 0.80 for 20% reduction (1 – 0.20).
- Copy that cell.
- Select cells with original numbers.
- Right-click > Paste Special > Multiply > OK.
This multiplies selected cells by 0.80 directly and overwrites originals. It works fast for one-time percentage subtraction.
Common Examples of Percentage Reduction in Excel
Example 1: Applying Discounts to Products
Original prices: $200, $150, $300. Reduce by 25%.
Use =original*(1-25%) → Results: $150, $112.50, $225.
This calculates discounted price or sale price.
Example 2: Budget Adjustment
Monthly budget: $5000. Reduce expenses by 10%.
Formula: =5000*(1-10%) = $4500 new budget.
Example 3: Salary or Tax Deduction
Gross salary $6000. Deduct 5% tax.
=6000*(1-5%) = $5700 net.
These show how subtract percentage helps in finance.
Tips for Accurate Percentage Calculations
- Format results as currency or numbers for clarity.
- Avoid errors by ensuring percentages are decimals (Excel handles % symbol).
- For negative results (rare), check inputs.
- Combine with functions like IF for conditions, such as no reduction if percentage is zero.
Percentage decrease differs from reducing the number. To find the decrease amount: =original - reduced.
Or the percentage change: =(reduced - original)/original.
But for simple reduction, stick to the main formula.
Advanced Use: Reducing Multiple Columns or Rows
When working with entire columns or long lists, Excel lets you apply percentage reductions efficiently. You can use the fill handle to drag the formula down or double-click it to automatically copy the formula to all adjacent rows.
In Excel 365 and Excel 2021, dynamic arrays make percentage reduction formulas even more efficient. A dynamic array allows a single formula to spill results automatically into multiple cells, removing the need to copy or drag formulas.
For example, if you have a list of prices in column A and want to reduce all values by 10%, you can enter one formula like:
=A2:A20*(1-10%)Excel automatically fills the results into the corresponding rows. If you add or remove values from the source range, the results update instantly.
This feature is helpful for large datasets, price lists, and financial models, as it keeps calculations clean, reduces errors, and saves time when working with percentage-based adjustments.
Frequently Asked Questions
What is the basic formula to reduce a number by a percentage in Excel?
The main formula is =original_number * (1 – percentage). For example, to reduce 100 by 20%, use =100*(1-0.20) or =A1*(1-B1) where A1 has the number and B1 has 20% formatted as percentage. This multiplies the original by the remaining percentage (80% in this case).
How do I apply the same percentage reduction to multiple cells in Excel?
Enter the formula in the first cell, like =B2*(1-$E$1) where E1 holds the fixed percentage. Use absolute reference ($) for the percentage cell. Then drag the fill handle down or across to copy the formula to other cells.
Can I reduce numbers by a percentage without using formulas in Excel?
Yes, use Paste Special. Enter the multiplier (like 0.80 for 20% reduction) in a cell and copy it. Select the numbers to reduce, right-click, choose Paste Special > Multiply > OK. This directly updates the selected cells.
Why is my percentage reduction formula giving wrong results in Excel?
Common issues include not formatting the percentage cell correctly (use Percentage format), typing the percentage as a whole number instead of decimal, or forgetting parentheses in the formula. Also, check for non-numeric data causing #VALUE! errors.
How do I format cells to show percentages correctly in Excel?
Select the cell or range, go to Home tab > Number group > click the Percentage button. This displays values like 20% as 0.20 internally for calculations but shows as percentage on screen.
What is the difference between reducing by percentage and calculating percentage decrease?
Reducing by percentage finds the new lower value (e.g., discounted price). Percentage decrease finds how much it dropped relative to original, using =(original – new)/original formatted as percentage.
Vaishvi Desai is the founder of Excelsamurai and a passionate Excel enthusiast with years of experience in data analysis and spreadsheet management. With a mission to help others harness the power of Excel, Vaishvi shares her expertise through concise, easy-to-follow tutorials on shortcuts, formulas, Pivot Tables, and VBA.