Plot No. 7 · Everyday & Shopping
Percentage Calculator
Find a percentage of any number, then see what that value looks like added on or taken off. Handy for discounts, tips, tax, markups and quick mental-maths checks.
To find a percentage of a number, multiply the number by the percentage and divide by 100.
The link saves your inputs so you can bookmark or share this exact result.
How the percentage calculator works
This calculator answers the most common everyday percentage question: what is a given percentage of a number. It multiplies your base value by the percentage and divides by 100 to find that part of the whole. It then shows two more useful views, the base with the percentage added on and the base with the percentage taken off.
Those three outputs cover most real situations in one screen. The part of the whole is what you need for a tip or a tax line, the increased figure mirrors a markup or a price plus tax, and the decreased figure is exactly how a sale discount works.
How to use the percentage calculator
- Enter the percentage you want to apply.
- Enter the value you want the percentage of.
- Read the three results: the percentage of the value, the value increased by it and the value decreased by it.
Worked examples
Twenty percent of 150
Inputs: Percentage 20, value 150.
Result: 20 percent of 150 is 30. The value increased by 20 percent is 180, and decreased by 20 percent is 120.
A VAT-style addition
Inputs: Percentage 20, value 49.99.
Result: The part is about 10.00, so adding it gives roughly 59.99, the kind of figure you get when adding 20 percent tax to a net price.
Limitations and common mistakes
Edge cases and limitations
- It handles a percentage of a number, not the reverse question of what percentage one number is of another, which needs a different formula.
- Results are shown to two decimal places, so very long decimals are rounded for readability.
- Negative percentages and negative bases are allowed and simply flip the direction of the increase and decrease, which can be confusing if entered by accident.
Common mistakes
- Confusing a percentage of a value with a percentage change between two values.
- Stacking increases and decreases and expecting them to cancel. A 20 percent rise then a 20 percent fall does not return you to the start.
Frequently asked questions
How do I work out a percentage of a number?
Multiply the number by the percentage, then divide by 100. For example, 20% of 150 is 150 times 20 divided by 100, which equals 30.
How do I add a percentage to a value?
First find the percentage amount, then add it to the original value. Adding 20% to 150 means adding 30, giving a total of 180.
How do I subtract a percentage from a value?
Find the percentage amount and subtract it from the original value. A 20% reduction on 150 removes 30, leaving 120. This is the maths behind a sale discount.
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