Mathematics
Percentage and general-purpose math calculators.
Mathematics calculators cover the kind of arithmetic that shows up constantly in everyday life and schoolwork alike, percentages, statistics, geometry, probability, that's simple in principle but easy to compute incorrectly under time pressure or when a problem's wording is ambiguous about which formula actually applies. This category includes percentage calculators (percentage of, percentage change, percentile), statistics calculators (variance, standard deviation, sample size, weighted average), geometry calculators (area and volume for common 2D and 3D shapes), and step-by-step arithmetic tools like long division that show their full working, not just a final answer. These are useful for checking homework, verifying a statistical claim, working out a geometry problem for a home-improvement project, or settling an argument about how a percentage change should actually be calculated. Where a concept has more than one accepted convention, like percentile calculation methods or sample versus population variance, the calculator is explicit about which one it uses and why, rather than presenting a single number as the only possible right answer.