Calculator guide
Solve common percentage questions such as a percent of a number, a change, or the rate one value represents.
Formula or method
Percent of = base×rate/100; percent change = (new−old)/old×100%; part rate = part/whole×100%.
How to use this calculator
- Choose the question type.
- Enter the values requested by that operation.
- Check whether the result is a percent, amount, increase, or decrease.
Worked example
A 15% discount on $80 is $80×.15=$12, so the sale price is $68.
Understanding the result
Percentage change uses the original value as its baseline; reversing the comparison can produce a different percentage.
Limitations and assumptions
- A zero baseline makes percentage change undefined.
- Rounding intermediate values can slightly change a final result.
Frequently asked questions
Is a 20% increase then 20% decrease zero?
No. $100 becomes $120 then $96; sequential percentages use different bases.
How do I find the original price?
Divide the final price by one plus or minus the rate, depending on the change.
Can percentages exceed 100%?
Yes, when a part is larger than its reference whole or a value more than doubles.
Sources
Educational information only; verify important decisions with a qualified professional.