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Everything you need to know about unit conversion — fast.
Covers everyday and specialist conversions: length, weight, temperature, speed, volume, area, pressure, energy, power, fuel economy, cooking measurements, time, frequency, angle, data storage, and number bases.
Results update as you type — no button to press. The multi-unit panel shows every unit in the selected category simultaneously so you can compare values at a glance.
Click any row in the results panel to copy that value straight to your clipboard. A confirmation tick confirms the copy. Works on desktop and mobile.
Every conversion is calculated through a shared base unit for each category. All length values convert through metres, and all weight values through kilograms. This ensures accuracy across any combination of units without a separate formula for every pair. Temperature is handled specially since Celsius, Fahrenheit, and Kelvin use offset formulas rather than simple multiplication.
Manual unit conversion is error-prone, especially across measurement systems or with unfamiliar units like Pascals or dBm. An instant converter eliminates rounding mistakes and removes the need to remember conversion factors. Whether you're cooking, travelling, studying, or working in engineering, having a reliable reference saves time and prevents costly errors.
Unlike most units, temperature scales don't share a common zero point, so you can't simply multiply. To convert Celsius to Fahrenheit: multiply by 9/5 then add 32. To convert to Kelvin: add 273.15. Kelvin is the SI base unit used in science because it starts at absolute zero — the point at which all molecular motion stops.
The metric system (SI) is used by most of the world and is based on powers of ten, making conversions straightforward. The imperial system — still common in the US and UK for everyday use — uses arbitrary factors (12 inches in a foot, 16 ounces in a pound). This converter handles both seamlessly, including hybrid units like miles-per-gallon alongside litres-per-100km.
What each category measures, the units it includes, and where you'd actually use it.
Covers metres, kilometres, miles, feet, inches, nautical miles and light-years. Metric length is defined off the metre, itself now fixed by the speed of light; imperial length still traces back to old body-based units like the foot. Useful for travel distances, construction measurements, and converting recipe or furniture dimensions between US and metric listings.
Kilograms, grams, pounds, ounces, stone and tonnes. Note that "weight" in everyday speech usually means mass, not the force of gravity a physicist would call weight. Common uses: reading nutrition labels, shipping/postage limits, gym plates, and converting a UK "stone" figure (common for body weight) into kilograms or pounds.
Celsius, Fahrenheit, Kelvin and Rankine. Celsius and Fahrenheit use offset scales, so conversion needs addition as well as multiplication — a common source of manual errors. Kelvin starts at absolute zero and is the scale used in physics and chemistry. Handy for weather, oven temperatures, and lab work.
Litres, millilitres, cubic metres, US gallons, quarts, pints, cups, fluid ounces and more. Note that a US gallon and a UK (imperial) gallon differ by about 20% — a frequent source of confusion when reading fuel economy or drink recipes from a different country.
m/s, km/h, mph, knots and Mach. Knots (nautical miles per hour) are standard in aviation and marine navigation because they align with degrees of latitude. Mach expresses speed relative to the local speed of sound, so a "Mach 1" conversion here uses the standard sea-level approximation.
Square metres, hectares, acres, square miles, square feet and more. Real estate listings, farming, and land surveying frequently mix acres and hectares, which is where rounding errors creep in most often — one hectare is roughly 2.47 acres.
Bits, bytes, kilobytes through petabytes, plus kilobits/megabits/gigabits for network speeds. A subtle trap: storage is usually measured in binary units (1 KB = 1024 B) while network bandwidth is usually decimal (1 Mbps = 1,000,000 bits/s) — which is why a "100 Mbps" connection never quite matches the download speed shown in your file manager.
Joules, calories, kilocalories, watt-hours, kilowatt-hours, electronvolts and BTU. Food labels use kilocalories but often just print "Calories" — this is the single most common source of a 1000x confusion in nutrition math. Electricity bills use kilowatt-hours, while HVAC and heating specs often use BTU.
Watts, kilowatts, horsepower (mechanical and metric), and BTU per hour/second. Car specs typically use horsepower, appliance labels use watts, and air conditioners are often rated in both watts and BTU/hr — this category bridges all three plus the reciprocating-refrigeration "ton" unit.
Pascal, bar, atmosphere, PSI, torr (mmHg) and more. PSI dominates in the US for tyre pressure and plumbing, bar is standard in most of Europe, and torr/mmHg still shows up in medicine (blood pressure) and vacuum engineering.
Degrees, radians, gradians, turns, arcminutes and arcseconds, plus NATO mils used in artillery and optics. Radians are the "natural" unit used throughout calculus and physics, while gradians (400 per full circle) appear in surveying.
From nanoseconds up to centuries, plus Planck time — the smallest physically meaningful time interval in current physics, roughly 5.4 × 10⁻⁴⁴ seconds. Most everyday use is seconds through years, but this range is useful for anything from computing benchmarks to historical timelines.
Teaspoons, tablespoons, cups, fluid ounces and the old-fashioned "pinch," "dash," and "smidgen" — approximated here at roughly 1/16, 1/8 and 1/32 of a teaspoon respectively, based on common culinary references. Handy for scaling recipes between US and metric cookbooks.
Decimal, binary, octal, hexadecimal, Base32, Base64-style digits, and Roman numerals. A staple for programmers reading memory addresses or colour codes in hex, and for anyone decoding a Roman numeral date on a building or film credit.
Hertz through terahertz, plus RPM, RPS, radians/second, BPM (music tempo) and frames per second. Bridges audio engineering, mechanical engine speeds, and video production in one place.
L/100km, km/L, US and Imperial MPG, and more. This is a reciprocal relationship, not a linear one — a higher MPG means lower L/100km, so it can't be converted with a simple multiplier the way most other categories can. Useful for comparing a car's advertised efficiency across regions.
The conversion factors used here match standard published values (NIST and SI reference tables) to at least 5–6 significant figures, which is sufficient for most everyday, academic, and engineering estimation purposes. For regulatory, legal, or safety-critical work, always verify against the authoritative standard for your field.
Small differences usually come down to rounding depth or which reference standard was used (e.g. exact vs. rounded conversion constants). This tool uses commonly accepted exact or near-exact constants and displays results to a sensible number of decimal places rather than truncating early.
No. All conversions run locally in your browser using JavaScript — nothing you type is transmitted to a server. The only thing saved locally is your light/dark theme preference, stored in your browser so it persists between visits. See the Privacy Policy for details.
Most conversions are linear (multiply by a fixed factor). Fuel economy in "distance per volume" (MPG, km/L) is inversely related to "volume per distance" (L/100km), so the underlying math uses a reciprocal calculation rather than a straight multiplier — otherwise the numbers would come out backwards.
A US gallon (3.785 L) is smaller than a UK/imperial gallon (4.546 L) by roughly 17%. This converter uses the US gallon as its "Gallon" unit in the Volume category, which is why UK fuel-economy comparisons sometimes need the separate "MPG (Imperial)" unit in the Mileage category instead.
Because everything runs client-side, the page will keep working after it loads even with an intermittent connection. It isn't currently packaged as a standalone offline app or embeddable widget.