Percentage Calculator — Find %, Increase & Decrease
This percentage calculator solves common percentage problems: find what percent of a number, calculate percentage increase, decrease, difference, and change between two values. Enter your numbers and get instant results with step-by-step formulas.
Percentage Calculator
Choose a calculation mode below to solve common percentage problems instantly.
Calculate what a specific percentage of a number is. For example, what is 15% of 200?
Frequently Asked Questions
How do you calculate a percentage of a number?
Multiply the number by the percentage divided by 100. Formula: Result = Number × (Percentage / 100). Example: 25% of 200 = 200 × (25/100) = 200 × 0.25 = 50.
How do you calculate percentage increase?
Percentage Increase = ((New Value - Old Value) / Old Value) × 100. Example: Price went from $80 to $100. Increase = (100-80)/80 × 100 = 25% increase.
How do you calculate percentage decrease?
Percentage Decrease = ((Old Value - New Value) / Old Value) × 100. Example: Price dropped from $100 to $75. Decrease = (100-75)/100 × 100 = 25% decrease.
What is the difference between percentage change and percentage difference?
Percentage change compares a new value to an old value (has direction: increase or decrease). Percentage difference compares two values without implying direction, using their average as the base: |A-B| / ((A+B)/2) × 100.
How do you find what percent one number is of another?
Divide the part by the whole and multiply by 100. Formula: Percentage = (Part / Whole) × 100. Example: 30 is what percent of 120? Answer: (30/120) × 100 = 25%.
Does a percentage increase followed by the same decrease return to the original?
No! A 20% increase followed by a 20% decrease gives you less than the original. Example: $100 + 20% = $120, then $120 - 20% = $96 (not $100). This asymmetry occurs because the decrease is calculated on the larger number.
How do you convert a fraction to a percentage?
Divide the numerator by the denominator, then multiply by 100. Example: 3/8 = 0.375 × 100 = 37.5%. Common fractions: 1/2 = 50%, 1/3 = 33.3%, 1/4 = 25%, 1/5 = 20%, 3/4 = 75%.
How do you convert a decimal to a percentage?
Multiply the decimal by 100 and add the % symbol. Example: 0.85 = 85%, 0.072 = 7.2%, 1.5 = 150%. To go from percentage to decimal, divide by 100: 42% = 0.42.
What is the formula for percentage?
The basic percentage formula is: Percentage = (Part / Whole) × 100. Related formulas: Part = Whole × (Percentage/100), Whole = Part / (Percentage/100). These three forms solve for any unknown given the other two values.
How do you calculate percentage in Excel?
For basic percentage: =Part/Whole (format cell as %). For percentage of a number: =Number*Percentage%. For increase: =(New-Old)/Old. For decrease: =(Old-New)/Old. Format the result cells as Percentage in Excel.
Percentage Formulas
Below are the six most common percentage calculations with their formulas and worked examples.
1. What is X% of Y?
Example: 25% of 200 = 200 × 0.25 = 50
2. X is what percent of Y?
Example: 30 is what % of 120? → (30 / 120) × 100 = 25%
3. Percentage Increase
Example: Price from $80 to $100 → (100 - 80) / 80 × 100 = 25% increase
4. Percentage Decrease
Example: Price from $100 to $75 → (100 - 75) / 100 × 100 = 25% decrease
5. Percentage Difference
Example: Difference between 40 and 60 → |40 - 60| / ((40 + 60) / 2) × 100 = 20 / 50 × 100 = 40%
6. Reverse Percentage (Find Original Value)
After increase: Original = New Value / (1 + X/100)
After decrease: Original = New Value / (1 - X/100)
Example: $120 after a 20% increase → 120 / 1.20 = $100 original
Common Percentage Mistakes to Avoid
Increase + Decrease Don't Cancel Out
A 20% increase followed by a 20% decrease does not return to the original value. Example: $100 + 20% = $120, then $120 - 20% = $96 (not $100). The decrease is calculated on the larger number.
Using the Wrong Base Number
"A is 50% more than B" and "B is 50% less than A" are different statements. If A = 150 and B = 100, A is 50% more than B, but B is 33.3% less than A. Always identify which number is the base (denominator) for your calculation.
Adding Percentages With Different Bases
You can't simply add percentages that have different base values. A 10% discount on one item and a 20% discount on another does not equal a 30% total discount. You must calculate each discount separately on its respective base price, then combine the dollar amounts.
Percentage Points vs. Percent Change
Going from 10% to 15% is a 5 percentage point increase but a 50% relative increase. These are very different statements. "Unemployment rose 2 percentage points" (from 5% to 7%) vs. "Unemployment rose 40%" (from 5% to 7%) describe the same change differently.
Common Percentage Reference Table
Quick reference for converting between fractions, decimals, and percentages.
| Fraction | Decimal | Percentage |
|---|---|---|
| 1/2 | 0.5 | 50% |
| 1/3 | 0.333... | 33.33% |
| 2/3 | 0.667... | 66.67% |
| 1/4 | 0.25 | 25% |
| 3/4 | 0.75 | 75% |
| 1/5 | 0.2 | 20% |
| 2/5 | 0.4 | 40% |
| 3/5 | 0.6 | 60% |
| 4/5 | 0.8 | 80% |
| 1/6 | 0.167... | 16.67% |
| 1/8 | 0.125 | 12.5% |
| 3/8 | 0.375 | 37.5% |
| 5/8 | 0.625 | 62.5% |
| 7/8 | 0.875 | 87.5% |
| 1/10 | 0.1 | 10% |
Tip: X% of Y always equals Y% of X. For example, 8% of 50 = 50% of 8 = 4. This trick makes mental math much easier.
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