Unit Conversions, Instantly

Convert Calc covers 15 unit categories: length (meters, feet, inches, miles, nautical miles, and more), weight (kilograms, pounds, ounces, stones, metric tons), temperature (Celsius, Fahrenheit, Kelvin, Rankine), area (square meters, acres, hectares, square feet), volume (liters, gallons, fluid ounces, cubic inches), and speed (km/h, mph, knots, meters per second). Additional categories include pressure (pascals, PSI, bar, atmospheres, mmHg), energy (joules, calories, kilowatt-hours, BTU), power (watts, horsepower, BTU/hour), data storage (bits, bytes, kilobytes through terabytes), frequency (hertz, kilohertz, megahertz, gigahertz), force (newtons, pound-force, kilogram-force), angle (degrees, radians, gradians), fuel economy (mpg, L/100km, km/L), and time (seconds, minutes, hours, days, weeks, years).

Across all 15 categories, Convert Calc provides over 1,150 unit pair pages — each one a dedicated converter with its own URL, formula, and optional rich content. Pages are generated at build time as fully static HTML, so they load fast on any connection and are straightforward to bookmark or share.

The search bar at the top of every page lets you reach any of the 1,150+ pairs immediately. Type a unit name, symbol, or abbreviation — "kg", "fahrenheit", "mph" — and matching pairs appear as you type. No need to browse categories or remember exact spelling. If you use the same conversions regularly, they are saved locally in your browser under Recent Conversions, so your most-used pairs are always one tap away without any account or sign-in required.

Convert Calc is free to use with no account or sign-in required. Conversion results are computed entirely in your browser using conversion factors loaded with the page. There are no server round-trips for calculations. Google Analytics is enabled to monitor site usage and performance, which you can control via our GDPR consent settings. No third-party advertising scripts are used.

Metric units (the International System of Units, or SI) use base-10 relationships — a kilometer is exactly 1,000 meters, a kilogram is exactly 1,000 grams. This makes arithmetic straightforward: move the decimal point. Imperial units (feet, miles, pounds, gallons) use irregular ratios inherited from historical conventions: 12 inches to a foot, 3 feet to a yard, 5,280 feet to a mile, 16 ounces to a pound. The United States is the only large economy still using imperial units for everyday measurement, while science, medicine, and engineering worldwide use metric. You can read more about how both systems are formally defined on the unit systems page.

All conversion factors are sourced from NIST SP 811 (the NIST Guide to the SI), the SI Brochure published by the Bureau International des Poids et Mesures (BIPM), and IEC 80000 for data storage units — the same references used in scientific and engineering work worldwide. Each converter page cites its source with a direct link so you can verify the factor independently. Results are computed at full floating-point precision and rounded to the most useful number of significant figures for the specific pair.

Yes. Convert Calc is a static website and works on any modern mobile browser — iOS Safari, Chrome for Android, Firefox Mobile, and others. The converter widget is touch-friendly, inputs are sized for on-screen keyboards, and the layout adapts to any screen width. Because all conversion data is bundled with the page rather than fetched at runtime, results are immediate even on slow mobile connections, and conversions continue to work in areas with intermittent signal.

Not currently. Currency exchange rates change continuously and require a live data feed, which conflicts with Convert Calc's design principle of bundling all data with the page for speed and offline use. Convert Calc covers only units with fixed, internationally defined conversion factors — the 15 physical measurement categories available from the length, weight, temperature, and other category pages.