Math calculators on CalcTool
Free math tools for everyday numbers—percentages, fractions, ratios, basic statistics, and expression evaluation. Open a card above or use the links below; answers update as you type. No account required.
Tools in this category
- Percentage calculator — percent of a number, add/subtract a rate, percent change, what percent one value is of another.
- Fraction calculator — add, subtract, multiply, divide; mixed numbers; simplified fraction and decimal.
- Ratio calculator — split a total by ratio parts (e.g. profit share 2:3:5).
- Standard deviation calculator — mean and sample or population standard deviation from a list of values.
- Scientific calculator — expressions with sqrt, trig, log, powers, and constants.
When to use which tool
Percentages fit tax, markup, sale tags, tips stated as a rate, and “up or down by X%.” Fractions fit exact rational answers and homework-style operations. Ratios fit allocating one pool of money or material by weights, not necessarily percents that sum to 100 yet.
Standard deviation summarizes spread in a data set (grades, measurements, samples). The scientific calculator is for one-off numeric expressions rather than lists.
Quick examples
20% off a $85 item → percentage tool, subtract 20% from 85 or find 20% of 85 for the discount amount. Split $10,000 profit with partners weighted 2:3:5 → ratio tool with total 10000 and parts 2:3:5.
Data set 2, 4, 4, 5, 5, 7, 9 → standard deviation tool for mean and sample SD. Expression sqrt(144)+2^5 → scientific tool.
Accuracy and limits
Display may round long decimals. Standard deviation here is descriptive statistics only—not hypothesis testing. The scientific page evaluates expressions you type; it is not a graphing or computer algebra system.
Frequently asked questions
Which math calculator should I use for a discount?
Use the percentage calculator—subtract a percent from the list price or find X% of Y for the dollar amount off.
When do I need fractions instead of decimals?
Recipes, construction cuts, and homework often want an exact reduced fraction; the fraction calculator simplifies automatically.
How is splitting a bill by ownership different from a tip split?
Use the ratio calculator when shares follow weights (2:3:5). Use the tip calculator when everyone pays an equal share of bill + gratuity.
What is the difference between sample and population standard deviation?
Sample uses n−1 in the variance denominator. Population uses n when you have the full group.
Does the scientific calculator use degrees or radians?
Trigonometry uses radians. Multiply degrees by pi/180 inside the expression if needed.
Are results stored on a server?
No. Calculations run locally in your browser.