How to use
- Pick a mode.
- Enter values.
- See the result.
FAQ
What is "20% off"?
80% of the original price, i.e. original ×(1 − 0.20). "X 折" means X/10 of the price (八折 = 80%).
How do I calculate percent increase?
(New − Original) ÷ Original × 100%. For example 80 to 100 is a 25% increase.
What percent is A of B?
A ÷ B × 100%. For example 30 of 120 is 25%. The tool returns the ratio directly.
Does −30% then +30% return to original?
No — the base changes, so the result is lower. 100 −30% = 70, then +30% = 91, not 100.
How do I compute tip or tax with percent?
Multiply the bill by the rate, e.g. 15% tip = amount × 0.15; the tool can also reverse "price including tax" to the pre-tax value.
How do I express margin as a percent?
Gross margin = (price − cost) ÷ price × 100%; use the ratio feature to get it quickly.
About this Percentage Calculator
Ratio = A/B*100%; after change = base*(1±p%); reverse = result/(1±p%). Runs locally.