Math

Math & Calculators brings together the everyday arithmetic people actually search for — not a scientific-calculator replica, but 47 focused tools that each answer one question well: what's 15% of this bill, how many days until that deadline, what will this mortgage cost per month, is 91 a prime number, what's the standard deviation of this dataset. Every calculator here runs entirely in your browser. There is no server round-trip between typing a number and seeing the result, which means results appear instantly and nothing you type — whether it's a salary figure, a due date, or a set of exam grades — is ever transmitted or stored. That matters more than it might seem: percentage and finance calculators are routinely used with real income, loan and health numbers, and this category is built so that data never has to leave your device to get an answer. The tools are grouped loosely by the kind of problem they solve. Everyday arithmetic covers percentages, fractions, ratios and ranges. Statistics covers averages, medians, modes, standard deviation and probability for anyone working with a dataset, a classroom assignment, or a quick sanity check on a spreadsheet formula. Number theory covers GCF, LCM, prime checking and prime factorization — small, exact tools that are surprisingly hard to do reliably by hand once numbers get past two or three digits. Finance covers the calculations people reach for most: VAT, discounts, tips, loans, mortgages, compound interest and profit margins, each using the standard formulas lenders and accountants actually use, shown transparently rather than hidden behind a black box. Life and date math covers ages, date differences, business days, pregnancy due dates and sleep cycles — calculations that involve calendar arithmetic most people would rather not do by hand (leap years, varying month lengths, and time zones all complicate this more than it first appears). Measurement and DIY covers concrete, paint, tile and BTU calculators for home-improvement projects where getting the quantity wrong means an extra trip to the store. Algebra covers quadratic equations and matrices for students and anyone who needs a step beyond basic arithmetic. Each calculator page includes a short explanation of the underlying formula, common pitfalls, and worked examples, so the tool doubles as a quick refresher on the math itself — not just an answer box. If you're unsure which tool covers your specific question, the search bar at the top of every page searches across all 47 titles, descriptions and FAQs at once.