How to Calculate Percentage Increase and Decrease (Formulas & Real Examples)
The exact step-by-step math for calculating percentage changes, markup differences, and Excel formulas without common arithmetic traps.
- What is the formula to calculate percentage increase between two numbers?
- How do you calculate percentage decrease with negative numbers?
- What is the difference between percentage change and percentage points?
- How do you write a percentage change formula in Microsoft Excel or Google Sheets?
1. The Core Percentage Change Formula
To find the percentage change between any initial value (V1) and a final value (V2), subtract the original value from the new value, divide that difference by the absolute value of the original number, and multiply by 100.
The denominator must always represent your starting point. If you accidentally divide by the new number instead of the original number, your calculation will be completely inaccurate.
2. Worked Example: Percentage Increase
Suppose your monthly cloud hosting bill was $80 in January and increased to $108 in February. How much did your expense increase in percentage terms?
Step 1: Compute the absolute difference: 108 - 80 = 28. Step 2: Divide by the starting baseline: 28 / 80 = 0.35. Step 3: Multiply by 100: 0.35 * 100 = 35% increase.
| Starting Value (V1) | New Value (V2) | Difference | Division (Diff / V1) | Final Percentage |
|---|---|---|---|---|
| $80.00 | $108.00 | +$28.00 | 28 / 80 = 0.35 | +35.0% |
| $500.00 | $625.00 | +$125.00 | 125 / 500 = 0.25 | +25.0% |
| 1,200 users | 1,920 users | +720 users | 720 / 1200 = 0.60 | +60.0% |
3. Worked Example: Percentage Decrease
Now examine a price reduction. A laptop originally priced at $1,200 is marked down to $840 on clearance.
Step 1: Compute the difference: 840 - 1200 = -360. Step 2: Divide by original price: -360 / 1200 = -0.30. Step 3: Multiply by 100: -0.30 * 100 = -30% (a 30% discount).
4. The Negative Number Trap (Baseline Direction)
A common mathematical error occurs when your starting value is negative. For instance, if an operating loss of -$20,000 becomes a profit of +$10,000, dividing by a negative denominator yields an incorrect negative percentage.
To prevent this distortion, always take the absolute value of the original number in the denominator: |V1|. In this scenario: (10,000 - (-20,000)) / |-20,000| = 30,000 / 20,000 = +150% improvement.
5. Percentage Change vs. Percentage Points
News reports and financial statements frequently confuse these two terms. An interest rate moving from 4.0% to 5.0% is an increase of 1.0 percentage point, but a 25.0% relative increase.
Always state "percentage points" when subtracting one percentage from another. Reserve "percentage change" for relative growth ratios.
6. Spreadsheet Formulas (Excel & Sheets)
In Microsoft Excel or Google Sheets, if cell A2 holds your initial number and B2 holds your updated number, write the formula as follows:
=(B2 - A2) / ABS(A2)Enter this formula into cell C2, then set the cell number format to Percentage.
Frequently Asked Questions
Direct answers to the most common questions people ask online about this topic.
Why does a 50% loss require a 100% gain to break even?
Because the baseline changes. If you start with $100 and lose 50%, you have $50 left. To return from $50 back to $100, you need to gain $50, which is 100% of your current $50 baseline.
Can percentage increase exceed 100%?
Yes. Any time a quantity more than doubles, the percentage increase is greater than 100%. For example, growing from 10 units to 35 units is a 250% increase.
How do I calculate percentage of a total instead of change?
Divide the specific portion by the total amount and multiply by 100. If 45 out of 180 survey respondents voted yes, 45 / 180 = 0.25 * 100 = 25%.