Percentages & Everyday Math
This section collects the arithmetic that comes up outside the classroom: percentages of a total, what share one number is of another, and how much a value rose or fell between two readings.
Every calculator prints the formula beside the answer, so the work can be copied into a spreadsheet or explained to a colleague instead of being taken on trust.
Calculators in this section
Complete alphabetical list · 20
- Aspect Ratio Calculatoraspect ratio calculatorOpen →
- Average Calculatoraverage calculatorOpen →
- Circle Area Calculatorcircle area calculatorOpen →
- Cylinder Volume Calculatorcylinder volume calculatorOpen →
- Fraction Calculatorfraction calculatorOpen →
- GPA Calculatorgpa calculatorOpen →
- Grade Calculatorgrade calculatorOpen →
- Ohm's Law Calculatorohms law calculatorOpen →
- Online Calculatoronline calculatorOpen →
- Percentage Calculatorpercentage calculatorOpen →
- Percentage Change Calculatorpercentage change calculatorOpen →
- Pythagorean Theorem Calculatorpythagorean theorem calculatorOpen →
- Quadratic Formula Calculatorquadratic formula calculatorOpen →
- Random Number Generatorrandom number generatorOpen →
- Ratio and Proportion Calculatorratio calculatorOpen →
- Rounding Calculatorrounding calculatorOpen →
- Scientific Calculatorscientific calculatorOpen →
- Square Root Calculatorsquare root calculatorOpen →
- Standard Deviation Calculatorstandard deviation calculatorOpen →
- Triangle Area Calculatortriangle area calculatorOpen →
What is in this section
- Percentage calculator: percent of a number, share as a percent, add or subtract a percent, and find the whole from a part.
- Percentage change calculator: how much a value increased or decreased between two readings.
Percent versus percentage point
These two are mixed up constantly. A percentage point is the gap between two percentages: a rate moving from 5% to 7% gains two points. The relative increase, however, is 40%.
In reports and headlines the choice of wording changes how the same numbers land, which is why it pays to convert between them quickly.
Rules that save time
- One percent is the number with the decimal point moved two places left.
- Percentages of different bases do not add up: 20% off and then 10% off comes to 28%.
- A rise and a fall of the same percent never return to the starting value.
- When the starting value is zero, percentage change is undefined — use the absolute difference.
Frequently asked questions
Which calculator should I use for a discount?
For a sale price, the discount calculator in the everyday money section is more direct; for arbitrary percentages, use the percentage calculator.
How is percentage change different from a percent of a number?
A percent of a number is a share of one value. Percentage change compares two values and reports the increase or decrease between them.
Do I need an account?
No. Everything runs in the browser, and a link to any result can be shared straight from the address bar.