Free Math Calculators

Quick helpers for percentages, statistics, factorials, primes, quadratics and geometry, each with the formula it uses.

• Percentage calculator – X% of Y = X × Y ÷ 100. X is what percent of Y = X ÷ Y × 100.
• Percent Change calculator – Percent change = (new − old) ÷ |old| × 100.
• Average & Statistics calculator – Mean = sum ÷ count. Median is the middle value. Standard deviation measures spread around the mean.
• Factorial calculator – n! = n × (n−1) × … × 1, and 0! = 1. It counts the ways to arrange n items.
• Prime & Factors calculator – A prime has exactly two factors, 1 and itself. Prime factorization splits a number into primes that multiply back to it.
• GCD & LCM calculator – GCD is the largest number dividing both; LCM = A × B ÷ GCD.
• Quadratic Equation calculator – For ax² + bx + c = 0, x = (−b ± √(b² − 4ac)) ÷ 2a. The discriminant b² − 4ac decides the number of real roots.
• Pythagorean Theorem calculator – In a right triangle, a² + b² = c², where c is the hypotenuse.
• Circle & Sphere calculator – Circumference = 2πr, circle area = πr², sphere volume = 4/3 πr³.
• Permutation & Combination calculator – nPr = n! ÷ (n−r)! when order matters. nCr = n! ÷ (r! × (n−r)!) when it does not.
• Triangle (Heron) calculator – With s = (a+b+c) ÷ 2, area = √(s(s−a)(s−b)(s−c)).