GIGACalculator.com: Online Calculators and Converters A comprehensive set of free online calculators and free online converters for your everyday calculations. Finance calculators, business calculators, health calculators, date and time calculators, mathematical, geometrical and trigonometry calculators, and so on. Converters between imperial and metric units, as well between units of the same system, but different scale. Well-sourced calculators and converters, formulas, explanations and advice.