About the percentage calculator
This percentage calculator answers the six questions people ask most often: what is X% of Y, X is what percent of Y, X is Y% of what number, what is the percentage change from A to B, how do I increase or decrease a number by a percentage, and what is the percentage difference between two values.
Choose the question that matches yours, fill in the numbers and see the answer with the working.
Who should use the percentage calculator
- Shoppers checking discounts and sale prices.
- Students and professionals working with growth rates, margins and changes.
- Anyone who forgets whether to divide or multiply.
How to use the percentage calculator: what each input means
- Question type
- Select the form of percentage problem you want to solve.
- Numbers
- The fields change to match the question, for example the percentage and the number, or the old and new values.
How the percentage calculator works: method and formula
A percentage is a fraction of 100. To find X% of Y you multiply Y by X ÷ 100. To find what percent a part is of a whole, divide the part by the whole and multiply by 100. For percentage change, subtract the old value from the new one, divide by the old value and multiply by 100.
Percentage difference is different from percentage change: it compares two values symmetrically, dividing the gap by their average, so neither is treated as the starting point.
- X% of Y
- result = Y × X ÷ 100
- Percent of a whole
- percent = part ÷ whole × 100
- Percentage change
- change = (new − old) ÷ |old| × 100
- Percentage difference
- diff = |a − b| ÷ ((|a| + |b|) ÷ 2) × 100
How to read your percentage calculator result
A positive change is an increase and a negative change is a decrease. Remember that a percentage rise followed by the same percentage fall does not return to the start: +50% then −50% leaves you 25% lower.
Percentage change is undefined when the starting value is zero.
Percentage Calculator worked example
Four common questions with simple numbers.
- 15% of 80 = 80 × 15 ÷ 100 = 12.
- 12 is what percent of 60? 12 ÷ 60 × 100 = 20%.
- From 250 to 300 is a change of (300 − 250) ÷ 250 × 100 = 20.0%.
- The percentage difference between 40 and 50 is 10 ÷ 45 × 100 = 22.22%.
15% of 80 is 12.
Practical uses of the percentage calculator
- Working out a sale price after a discount.
- Finding a percentage increase in salary, price or traffic.
- Comparing two values without choosing a baseline.
Assumptions and limitations of this calculator
- Does not know context, such as percentage points versus percent. A rise from 2% to 3% is 1 percentage point, or a 50% relative increase.
- Compound or successive percentage changes should be calculated one step at a time.