Choose the question, then type two numbers per line. You can enter many lines at once, for example a price list with the same discount. Everything is calculated in your browser.
Percentage calculator is a free online tool by Hack the Hydra. Calculate X% of a number, what percent one number is of another, percentage change, and add or subtract a percentage. One calculation per line, free and private.
The five formulas
A% of B is B x A / 100. "A is what percent of B" is A / B x 100. Percent change from A to B is (B - A) / A x 100, positive for an increase and negative for a decrease. Increasing B by A% multiplies B by (1 + A/100), and decreasing multiplies by (1 - A/100).
Discounts and VAT
For a 20% discount on 80, choose "Decrease B by A%" and enter 20 80 to get 64. To add 21% VAT to a net price of 150, choose "Increase" and enter 21 150 to get 181.5. To get the net price back from a gross price, divide by 1.21 instead: decreasing the gross price by 21% does not undo a 21% increase.
Percent change is not symmetric
Going from 100 to 150 is +50%, but going from 150 back to 100 is -33.33%, because the base changes. This is why a 50% gain followed by a 50% loss leaves you below where you started. Percentage points are a different thing: moving from 10% to 12% is +2 points but +20% in relative terms.
Example
Percentage change, one pair of numbers per line (old value, new value).
Input
80 100
100 80
Output
From 80 to 100: +25%
From 100 to 80: -20%
How to use
- Pick the type of calculation.
- Type two numbers per line, separated by a space, comma or semicolon. Decimal comma is accepted.
- Read the result next to each line and copy it.
FAQ
Can I calculate several values at once?
Yes, put one calculation per line. Each line gets its own result.
Does it accept a decimal comma?
Yes, 7,5 is read as 7.5. Do not use thousands separators; write 1200, not 1,200.
Why does the change from 150 to 100 differ from 100 to 150?
Because the percentage is always relative to the starting value. The start is different in the two cases.
How do I find the original price before a discount?
Divide the discounted price by (1 - discount/100). For a final price of 64 after 20% off, 64 / 0.8 = 80.
Guides
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