A part as a percentage of the whole
Divide the part by the whole and multiply by 100. A percentage is undefined when the whole is zero.
If 12 of 30 respondents choose an option, the result is 40%.
- Percentage = part ÷ whole × 100
- Part = whole × percentage ÷ 100
Change rate uses the earlier value
A rise from 80 to 100 is a difference of 20 but a 25% increase because 80 is the base. A fall from 100 to 80 is 20%.
The same absolute difference can produce asymmetric rise and fall rates when the bases differ.
Example: 20% off, then another 10%
A 100,000-won price becomes 80,000 won after 20% off, then 72,000 won after another 10%. The effective discount is 28%, not 30%.
The result also depends on whether a coupon is fixed or percentage-based and when it is applied.
- First price = original × (1 - first rate)
- Final = first price × (1 - second rate)
- Effective rate = savings ÷ original × 100
Confirm checkout conditions
Shipping, tax, minimum purchase, and discount caps may sit outside the basic calculation. Confirm the final checkout amount.
When reporting a change rate, include both the comparison period and the base value.