Math calculators

Everyday math

Percentages. Percentages are the most-used piece of school maths in adult life — discounts, tax, tips, interest and growth rates all rely on them. There are three standard questions our percentage calculator answers: what is X% of a number (result = number × percent ÷ 100, so 15% of 200 = 30), what percent one number is of another (part ÷ whole × 100), and the percentage change between two values (((new − old) ÷ old) × 100). Reversing a percentage — finding the original price before a discount — is just as common: original = result ÷ (percent ÷ 100). The calculator handles fractional rates such as 12.5% and shows each step. Fractions. Adding, subtracting, multiplying and dividing fractions trips up many learners because the rules differ for each operation. To add or subtract you first bring both fractions to a common denominator; to multiply you multiply numerators and denominators directly; to divide you multiply by the reciprocal. The fraction calculator simplifies the result to lowest terms using the greatest common divisor and can convert between improper fractions, mixed numbers and decimals — showing the intermediate steps so it doubles as a learning aid. Geometry — area and volume. Every shape has its own formula: rectangle a × b, triangle (a × h) ÷ 2, circle π × r², trapezium ((a + b) ÷ 2) × h, parallelogram a × h. For solids the volume calculator covers the cuboid (a × b × c), cylinder (π × r² × h), sphere ((4 ÷ 3) × π × r³) and cone ((1 ÷ 3) × π × r² × h). Enter the dimensions in any consistent unit (cm, m, mm) and the tool returns the area or volume plus, for 3D solids, the surface area. Number theory and equations. The GCD/LCM calculator uses the Euclidean algorithm — GCD(a, b) = GCD(b, a mod b) until the remainder is zero — and derives the least common multiple as (a × b) ÷ GCD. This is the backbone of simplifying fractions and solving proportions, where a ÷ b = c ÷ d gives d = (b × c) ÷ a. The quadratic equation calculator computes the discriminant Δ = b² − 4ac and returns the real roots with the full working. Alongside these you will find tools for averages, roots and powers, rounding, factorials and combinations, and binary–decimal–hexadecimal conversion. Every math calculator on Liczbnik is free, works directly in the browser without registration, and is built to show the steps rather than just a final number — so you can both get the answer and understand how it was reached.