Basic math calculators

Basic math is the kind that comes up constantly outside school: figuring out a tip, checking a percentage discount, splitting a bill, comparing two ratios, double-checking what your phone calculator just told you. The tools here cover the everyday arithmetic that doesn't belong to any specialised domain — fast, focused, and showing the formula next to the answer so you can spot if you typed the wrong number.

The percentage calculator is the most-used tool in the bunch. It handles the four common operations as separate modes: percent of a number, what percent A is of B, the percentage change between two numbers, and the original value before a known percentage change. Adjacent are the tip calculator (with bill split), the fraction calculator (add, subtract, multiply, divide with simplified output), the ratio calculator for solving proportions, and the exponent calculator covering integer, negative, and fractional exponents (cube roots, fourth roots) that most pocket calculators handle awkwardly.

For number-theoretic curiosities, the GCD/LCM calculator handles two or more numbers at once via the Euclidean algorithm, and the prime checker tests primality up to roughly 15 digits with the Miller-Rabin test. The Roman numeral converter goes both directions for any value 1-3999. For random tasks, the dice roller handles polyhedral dice (d4 through d100) and the random number generator draws integers in any range with optional no-duplicates mode.