To calculate percentage increase, subtract the original value from the new value, divide by the original value, then multiply by 100. For example, going from 50 to 75 is a 50% increase because ((75 − 50) ÷ 50) × 100 = 50.
This guide walks through the formula with three worked examples, shows the most common mistakes, and gives you a free calculator to skip the manual math.
The Percentage Increase Formula
That's it. Three steps:
- Subtract: New value − Original value = the difference.
- Divide: Difference ÷ Original value = the decimal change.
- Multiply: Decimal change × 100 = the percentage.
If the result is positive, it's an increase. If it's negative, it's a decrease.
Example 1: A Simple Price Increase
A product cost $40 last year and costs $52 this year. What's the percentage increase?
The price went up 30%. That means the new price is 130% of the original price (100% + 30%).
Example 2: A Salary Raise
Your salary went from $3,200/month to $3,600/month. What percentage increase is that?
Example 3: Website Traffic Growth
Your website had 8,500 visitors in September and 12,750 visitors in October. What's the growth percentage?
How to Calculate Percentage Decrease
Use the exact same formula. The result will be negative — that's your signal it's a decrease. Drop the minus sign and call it a "20% decrease" instead of "−20%".
Common Mistakes to Avoid
- Dividing by the new value instead of the original. Always divide by the original — that's the reference point. Dividing by the new value gives the wrong answer.
- Forgetting to multiply by 100. Without × 100, you get a decimal (0.30) instead of a percentage (30%).
- Confusing "increased by X%" with "X% of." An increase of 30% means new = original × 1.30. A value that is 30% of something is much smaller.
- Mixing up percentage increase and percentage difference. Percentage increase uses the original as the base. Percentage difference uses the average of both values.
Reverse-check: If a 30% increase takes $40 to $52, then a 30% decrease from $52 should take it back to $40. But 52 × 0.70 = $36.40, not $40. This is because the base changed. Always track your base value.
Skip the Math — Use a Calculator
If you need to do this often, or you just want a reliable answer without mistakes, use our free percentage calculator. It handles percentage increase, percentage decrease, and three other common percent problems instantly.
📊 Free Percentage Calculator
Calculate percentage increase, decrease, and more — instantly, in your browser.
Open Percentage Calculator →Frequently Asked Questions
Can percentage increase be more than 100%?
Yes. If a value doubles, the increase is 100%. If it triples, the increase is 200%. There is no upper limit — if you go from 1 to 1,000, that's a 99,900% increase.
What's the difference between percentage increase and percentage change?
They use the same formula. "Percentage change" is a broader term that covers both increases (positive result) and decreases (negative result). "Percentage increase" is specifically for upward changes.
How do I find the original value if I only know the percentage increase?
Divide the new value by (1 + percentage increase ÷ 100). Example: if a value increased 25% to reach 250, the original was 250 ÷ 1.25 = 200.
What if the original value is negative?
Percentage increase with negative values is mathematically tricky and rarely meaningful. For example, going from −10 to −5 is technically a 50% increase, but this confuses most people. In these cases, use absolute values or reframe the question.
How do I calculate average percentage increase over multiple periods?
Don't average the percentages directly — that gives the wrong answer. Instead, multiply the growth factors. Example: 10% increase, then 20% increase = 1.10 × 1.20 = 1.32 = 32% total, not 30%.