Percentage Calculator
Three modes in one tool: what is X% of Y, X is what percent of Y, and the percentage increase or decrease between two numbers.
Math Calculators
Percentages, fractions, ratios, roots, probability, standard deviation and area — with the working shown, not just the answer.
10 free calculators
Math & Statistics
Percentages, fractions, ratios, roots, probability, standard deviation and area — with the working shown, not just the answer.
These are the general-purpose tools — the ones that turn up inside every other category. A margin is a percentage, a mix is a ratio, a material estimate is an area, and an A/B test result is a standard deviation away from being meaningless.
The percentage calculator is the most used page on the site, and it runs three modes because "percentage" means three different sums: what is 15% of 240, 36 is what percent of 240, and what is the percentage change from 240 to 276. Mixing up the second and third is the origin of most of the percentage-point confusion in the news.
Fractions and ratios handle the everyday proportional work — halving a recipe, simplifying 18:24, scaling a mix, converting between a ratio, a fraction and a percentage. Exponents and roots cover the powers side, including fractional exponents and simplified radical form.
The statistics pair is where most people get value they did not expect. The average calculator returns mean, median, mode and range together, because a mean alone hides skew — a five-figure outlier in a small dataset moves the mean and leaves the median untouched, and the gap between them tells you something. The standard deviation calculator adds spread, and forces the sample-versus-population choice that most tools quietly make for you.
Rounding out the shelf: the probability calculator for independent, dependent, union, intersection and at-least-once events; the scientific calculator with trigonometry, logarithms and factorials, parsed by a purpose-built tokenizer rather than by evaluating your input as code; and the area calculator for eight shapes with unit conversion built in.
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All 10 math calculators
Fraction Calculator
Add, subtract, multiply and divide fractions with automatic simplification, mixed-number conversion and a decimal equivalent.
Average Calculator
Paste a list of numbers and get mean, median, mode, range, count and sum together, so outliers cannot hide behind the mean.
Ratio Calculator
Simplify a ratio, solve for a missing term, scale a recipe or mix, and convert between ratio, fraction and percentage.
Scientific Calculator
A full keypad with trigonometry, logarithms, powers, roots, factorials and constants, parsed safely without ever using eval.
Exponent Calculator
Raise any base to any power, including negative and fractional exponents, with scientific notation for very large results.
Square Root Calculator
Find square roots, cube roots and any nth root, with simplified radical form and a perfect-square check for whole numbers.
Probability Calculator
Compute single-event, union, intersection, complement and at-least-once probabilities for independent and dependent events.
Standard Deviation Calculator
Get population or sample standard deviation, variance, mean and standard error from a dataset, with every step shown.
Area Calculator
Calculate area for eight shapes — square, rectangle, triangle, circle, trapezoid, parallelogram, ellipse and sector — in any unit.
How to choose the right tool
Sample or population standard deviation? This is the one choice on this page that changes an answer materially. Use the population formula, dividing by N, when your data is the entire group you care about — every employee, every order last month. Use the sample formula, dividing by n − 1, when your data is a subset you are using to estimate something larger. Sample is the right default in almost all real-world work, and on small datasets the difference is large: with ten values, dividing by 9 instead of 10 raises the result by about 5%.
Average or standard deviation? Use both. The mean tells you where the centre is; the spread tells you whether the centre means anything. Two teams with the same average response time can have completely different customer experiences.
Percentage or ratio? Use a percentage when comparing a part with a whole, and a ratio when comparing parts with each other. A 2:1 mix and a 66.7% concentration describe the same thing, but only one of them scales cleanly when you need three times as much.
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Math questions
Subtract the old value from the new one, divide by the old value, then multiply by 100. Going from 240 to 276 is (276 − 240) ÷ 240 × 100 = 15%. Note the divisor is always the original value; dividing by the new one is a common and expensive slip.
A rise from 4% to 6% is a two percentage point increase and a 50% increase. Both statements are true and they sound very different, which is why the distinction is worth being precise about whenever a rate is being reported.
Because the mean is pulled by extreme values and the median is not. In salary data the mean usually sits well above the median, since a small number of very high earners lift the average without changing the midpoint. The average calculator shows both side by side.
Yes. It parses your input with its own tokenizer and shunting-yard evaluator, and it never uses eval or any other mechanism that would execute the text as code. Anything it cannot parse produces a plain error message rather than a result.
Calculate the probability it never happens, then subtract from one. For a 1-in-6 event over four attempts, that is 1 − (5/6)⁴ = 51.8%. The probability calculator has this as a dedicated mode, because doing it directly is far more error-prone.
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