Calculators
Everyday and technical maths: percentages, ratios, fractions, primes, geometry and a proper expression parser (no eval). Also the research statistics set — sample size, A/B significance, correlation and t-tests with real p-values.
Scale CalculatorConvert between real-world and drawing dimensions at any scale (1:50, 1:100, custom) for architecture and models.Feet & Inches CalculatorAdd, subtract and convert feet and inches with fractions, and switch to centimetres or metres — in your browser.Roof Pitch CalculatorConvert roof pitch between rise/run, degrees, percentage and x-in-12 — handy for roofing and construction.Stair CalculatorCalculate the number of steps, riser height, tread depth and total run from a total rise, with comfort checks.Triangle SolverSolve any triangle from its known sides and angles (Pythagoras, law of sines and cosines) and get the area.Scientific CalculatorA full scientific calculator with trigonometry, logarithms, powers, roots and constants — runs in your browser.Statistics CalculatorGet mean, median, mode, range, variance, standard deviation and quartiles from a list of numbers, instantly.GPA CalculatorAdd your courses, grades and credit hours to calculate your weighted GPA on a 4.0 scale — in your browser.Quadratic Equation SolverSolve ax²+bx+c=0 for real or complex roots, with the discriminant, vertex and axis of symmetry.Fraction CalculatorAdd, subtract, multiply and divide fractions, simplify them, and convert to mixed numbers or decimals.GCD & LCM CalculatorFind the greatest common divisor and least common multiple of several integers, with the Euclidean steps.Unit Price CalculatorCompare up to three products by price per unit and instantly see which is the best value. Enter each price, quantity and unit — the cheapest is highlighted.Ratio CalculatorSimplify ratios like a:b or a:b:c to their lowest terms with the GCD, and solve proportions a:b = c:x for the missing value. Decimals are supported.Permutations & CombinationsCompute permutations nPr and combinations nCr from n and r, with the factorial formulas shown. Exact whole-number results, even for large n.Prime FactorizationBreak any positive integer into its prime factors in exponent form (e.g. 360 = 2³ × 3² × 5), count its divisors, list them, and test whether the number is prime.Sample Size CalculatorFind how many survey responses you need from confidence level, margin of error and population size, with finite-population correction.A/B Test Significance CalculatorCheck whether your A/B test result is statistically significant: conversion rates, uplift, z-score, p-value and a plain-language verdict.Correlation CalculatorPaste paired data to get Pearson r, r², Spearman rho and covariance, with a scatter plot and plain-language interpretation.t-Test CalculatorRun a Welch two-sample or one-sample t-test: means, standard deviations, t statistic, degrees of freedom, exact two-tailed p-value and Cohen’s d.