Percentages compare a part with a whole on a scale of 100. Every percentage problem has three quantities (the part, the whole and the percentage), and you always know two of them. Choose the question you need to answer and enter the two numbers you know.
How to use the Percentage Calculator
- What do you want to calculate?
- Percentage (p)
- Number (x)
- Whole (y)
- Increase or decrease?
Results update as you type, and everything is calculated in your browser.
How it works
Each question rearranges the same relation part = whole × percentage ÷ 100. For increases and decreases the new value is the original multiplied by (1 + p/100) or (1 − p/100).
Inputs explained
| Field | What to enter |
|---|---|
| What do you want to calculate? | Choose one: What is p% of x?, x is what percent of y?, x is p% of what?, x increased / decreased by p% |
| Percentage (p) | In % |
| Number (x) | A number |
| Whole (y) | A number |
| Increase or decrease? | Choose one: Increase, Decrease |
What each result means
- p% of x = [Number (x)]×[Percentage (p)]÷100
- x as a percentage of y = [Number (x)]÷[Whole (y)]×100
- The whole (x is p% of it) = [Number (x)]×100÷[Percentage (p)]
Example values
How the main result changes when Percentage changes and everything else stays at the example values above:
| Percentage (p) (%) | p% of x |
|---|---|
| 7.5 | 6 |
| 11.25 | 9 |
| 15 | 12 |
| 18.75 | 15 |
| 22.5 | 18 |
| 30 | 24 |
Formula
p% of x: y = x × p ÷ 100
x is what % of y: p = x ÷ y × 100
x is p% of what: y = x × 100 ÷ p
x increased/decreased by p%: y = x × (1 ± p/100)
Worked example
Inputs: What do you want to calculate?: What is p% of x?; Percentage (p): 15 %; Number (x): 80.
Results: p% of x = 12.
Key terms
- Part
- The amount that is a percentage of the whole.
- Whole (base)
- The reference amount that represents 100%.
Frequently asked questions
How do I calculate 15% of 80?
Multiply 80 by 15 and divide by 100: 80 × 15 ÷ 100 = 12.
How do I find what percent one number is of another?
Divide the part by the whole and multiply by 100: 80 ÷ 320 × 100 = 25%.
How do I find the whole when I know a percentage?
Divide the part by the percentage and multiply by 100: if 12 is 15%, the whole is 12 × 100 ÷ 15 = 80.
Is a 20% increase followed by a 20% decrease zero change?
No. 100 × 1.2 × 0.8 = 96, a 4% loss overall.
Sources
Guides on this topic
- How to Calculate a Tip: Mental Math, Splitting and Tipping Norms: Use the 10% trick to work out any common tip in your head, decide whether to tip before or after tax, and split a group bill fairly.
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- How to Calculate Percentage: Formulas, Examples and Common Traps: Part divided by whole, times 100. Here is how to use that one idea for discounts, pay rises, tax, percent change and percentage points.