calculate.at

calculate.at is a free, ad-supported library of 290+ online calculators spanning finance, health, math, science, construction, unit conversion, date/time, and a handful of games. Every calculator runs directly in the browser — no signup, no download, no paywall on any tool — and returns a result instantly as you type or on a single click, depending on the calculator. The catalog is organized into eight categories: finance (loans, mortgages, tax, salary, investment), health (BMI, calories, hydration, body composition), math (percentages, fractions, equations, general arithmetic helpers), science (physics formulas, engineering calculations), construction (material quantities, area, cost estimates), unit conversion (length, weight, temperature, volume, and more), date and time (differences, countdowns, business-day math), and a small games section. New calculators are added on a rolling basis rather than as periodic batch releases. One deliberate design choice runs through the whole site: narrow, single-purpose pages instead of broad multi-function widgets. Unit conversion is the clearest example — miles-to-km and km-to-miles are two separate pages, each tuned to exactly the query that led there, rather than one generic converter with a direction dropdown buried in the middle. The same philosophy shapes most of the catalog: each calculator solves one specific question well instead of trying to cover many loosely related ones inside a single interface. Most calculators support two features aimed at making results genuinely shareable and reusable. First, results can be shared via a direct link — the calculator's inputs get encoded into the URL, so sending someone a link reproduces the exact same numbers they'd need to check or reuse, rather than making them re-enter everything from scratch. Second, a growing subset of calculators can be embedded on third-party sites as a live, working widget (not a static screenshot) via a simple iframe snippet. Embedding is a manual, free request process: a site owner picks a calculator, submits its URL through an embed request form, and gets back a ready-to-paste snippet by email, usually the same day. The embed carries a small attribution footer back to the source calculator page — that's the only thing that can't be stripped out, since it's how the embedding stays free. On top of the standard embed, calculate.at also takes customization requests: adjusting an existing calculator's fields or logic, translating one into another language, or — if nothing on the site already covers a specific use case — building a new calculator from scratch on request. There's no pricing tier anywhere on the product. The business runs on advertising rather than subscriptions, freemium gates, or a paid upgrade path, so every calculator — current and future — stays fully usable without an account or a credit card. That's a structural choice, not a temporary launch promotion: nothing on the roadmap moves behind a paywall later. calculate.at is built and maintained on an ongoing basis, with the catalog, embed feature set, and individual calculator content (worked examples, FAQs, formula explanations) all still actively expanding.