Math and Percentage Calculators

Which calculator do you need?

Percentages. Use the percentage calculator for “what is P% of a number” and “what percent is A of B,” and the percentage increase calculator when something has changed from an old value to a new one, or when you need to undo a change. The discount calculator adds stacked discounts and sales tax for shopping, the tip calculator handles the restaurant check and splitting it, and the percent error calculator compares a lab result with the accepted value.

Fractions, ratios and numbers. Convert either way with the decimal to fraction and fraction to decimal calculators; both handle repeating decimals exactly. Reduce a fraction or find a common denominator with the simplify fractions calculator, and do arithmetic with the mixed fraction calculator. The GCF and LCM calculators show the factoring behind all of these, and the factor calculator lists every factor of one number with its prime factorization. The ratio calculator simplifies ratios, solves proportions and splits totals, and the aspect ratio calculator applies the same math to screens, video and photos. For working with numbers themselves, the rounding calculator rounds to any place with the school rule or round half to even, the long division calculator shows each step of a division with a remainder or a decimal, the modulo calculator gives a mod n in the floored, truncated and Euclidean conventions, and the scientific notation calculator converts between decimal, e-notation and engineering notation and rounds to significant figures.

Algebra. The scientific calculator evaluates a typed expression with trig functions, logarithms, powers, roots, factorials and combinations, in degrees or radians, using the same order of operations the textbooks teach. The square root calculator simplifies radicals such as √72 = 6√2, the exponent and log calculators handle powers and logarithms in any base, and the quadratic formula calculator gives exact and complex roots with the vertex. The system of equations calculator solves two or three linear equations exactly, the slope calculator turns two points into a line equation, and the number sequence calculator finds any term and the sum of an arithmetic or geometric sequence, or identifies the pattern from a few terms.

Geometry. The Pythagorean theorem calculator finds the missing side of a right triangle, and the right triangle calculator solves its sides and angles with sine, cosine and tangent. The triangle calculator solves any triangle with the law of sines and the law of cosines, including the two-answer SSA case. The area and volume calculators cover common shapes and solids, with results in square and cubic feet, acres, gallons and metric units.

Statistics and probability. Start with the average calculator for the mean, median and mode, then use the standard deviation calculator for spread and the z-score calculator to see where one value sits; the mean absolute deviation calculator gives a simpler measure of spread. The quartile calculator gives the five-number summary, the IQR and outliers with a box plot, and the percentile calculator finds the value at any percentile or the percentile rank of a value. For inference, the confidence interval calculator builds z, t and proportion intervals, the sample size calculator works backward from a target margin of error, and the linear regression calculator fits a line of best fit with r and r². The probability calculator covers the and, or and conditional rules for two events and repeated tries, the permutation and combination calculator counts selections and arrangements, the expected value calculator finds the mean and standard deviation of a probability distribution, and the random number generator draws fair whole numbers or decimals in your browser, with or without repeats.

The methods follow open college textbooks from OpenStax, such as Prealgebra 2e, Algebra and Trigonometry 2e and Introductory Statistics 2e, which are linked on each page along with the worked examples the calculators reproduce.