Unit converter

What is it actually for, day to day?

For the traveler landing in New York who must read a dashboard in miles, a forecast in Fahrenheit and a tank in gallons. For the cook facing an American recipe in ounces, cups and °F, or a British one in imperial pints. For the student in physics, chemistry or medicine checking an order of magnitude — joules, moles, pascals, becquerels — without opening a constants manual. For the DIYer drilling a 6 mm hole with an inch bit, or setting a torque wrench graduated in lbf·ft. For the salesperson pricing freight in tons, pounds and cubic feet. In short, every time a number carries a unit you don't use, this tool translates it.

How is it different from other converters?

The converter built into a search engine answers fast, but one question at a time: it gives “62.14” without saying where the number comes from, with no table, no alternative, and no offline mode. Legacy mega-converters show hundreds of units buried in pages overloaded with ads, links and machine-translated text, where every conversion takes three clicks and a reload. Mobile apps demand an install, an account, and often a subscription to unlock “pro” categories like energy or pressure.

Volade takes the opposite stance on every point: a single page for 42 categories, zero reloads (everything recalculates as you type), the formula shown under every result for verification, the full table for the category at a glance, no account and no limits, and no data in transit since everything is computed in your browser. Add two calculators the others lack — degrees ↔ DMS and SPL decibels — plus a local history of your last 12 conversions, and you get a tool designed for converting, not for displaying ads.

Why is it the best? Five concrete reasons

1. Accuracy first. Every factor follows the official definition: the inch to within 2.54 cm, the pound to within 0.45359237 kg, the mile to within 1,609.344 m. Temperatures use their true offsets, and the four debatable conventions (mean month, Mach, thermochemical calorie, ISO BTU) are stated in black and white under the tool.

2. Total transparency. The formula accompanies every result — “10 km × 1.609344 = 16.09344 mi” — and the table shows the same value in all units. You never have to take the tool's word for it: you can recheck every figure with a calculator.

3. Useful exhaustiveness. 42 categories cover school needs (length, mass, time), the kitchen (US and imperial volumes), the garage (pressure, torque, power), the engineering office (stress, viscosities, flow) and the laboratory (moles, radioactivity, photometry). One tool, one habit.

4. Real privacy. No typed value ever leaves your device: there is no conversion server, so nothing to hack, nothing to resell, nothing to profile. History lives in your browser and clears in one click.

5. Speed and simplicity. No reloads, no banners to close, no tutorial: one category, one value, two units. The 14 popular shortcuts (10 km → mi, 25 °C → °F, 1 bar → psi…) handle 90% of needs in one click.

Free, really? And what is Premium?

Yes, truly free and unlimited: all 42 categories, all 353 units, the tables, local history and 1-click copy are available with no account, no quota and no credit card. There is no “5 conversions per day” and no locked categories. Volade Premium is not a toll on this tool: it is the global license for the ecosystem — browser, CMS, desktop, mobile, scripts and all web tools — that funds development. For the converter, it unlocks two comforts: unlimited history synced across your devices and PDF/CSV export of tables for your quotes and files. The free version stays complete for converting; Premium is for keeping and sharing.

Unit converter: the complete conversion guide

Converting a unit means expressing the same quantity in another system: you multiply by a conversion factor, a fixed ratio between two units. 1 inch is exactly 2.54 cm, 1 pound exactly 0.45359237 kg, 1 mile exactly 1,609.344 m: these definitions are not approximations, they are international conventions. The Volade converter applies them all, instantly, across 42 categories — and shows the formula so you can verify every result.

Temperature: the °C ↔ °F table to know

Temperature is the only common case that is not a simple factor: you must add an offset. Formulas: °F = (°C × 9/5) + 32 and °C = (°F − 32) × 5/9. For kelvins: K = °C + 273.15.

Length: km, miles, feet, inches

Construction, travel and sewing use three coexisting systems: metric, imperial and US. Remember 1 m = 3.28084 ft, 1 ft = 30.48 cm, 1 in = 2.54 cm.

Mass: kg, pounds, ounces

Cooking, fitness and freight juggle grams and pounds. Formula: lb = kg × 2.20462 and oz = g ÷ 28.349523125.

Volume: liters and gallons (US vs imperial)

The classic trap: 1 US gallon = 3.785411784 L but 1 imperial gallon = 4.54609 L, a 20% gap. Same logic for quarts, pints and fluid ounces.

Pressure: bar, psi, atm

Tires, compressors, diving: 1 bar = 14.5038 psi = 100 kPa and 1 atm = 1.01325 bar. At 10 m deep, pressure is about 2 absolute bar (1 bar of air + 1 bar of water).

Speed: km/h, mph, knots

On road and at sea: mph = km/h × 0.621371 and 1 knot = 1.852 km/h (one nautical mile per hour).

Energy and power: kWh, joules, horsepower

Electricity bill, engine, sport: 1 kWh = 3,600,000 J, 1 cal = 4.184 J, 1 cheval (ch) = 735.5 W versus 1 horsepower (hp) = 745.7 W — the two “horsepowers” are not equal.

Area: m², square feet, hectares

Real estate and farming: 1 m² = 10.7639 ft², 1 hectare = 2.47105 acres, 1 acre = 4,046.86 m².

Force and torque: newtons and pound-force

Mechanics and DIY: 1 lbf = 4.44822 N and 1 N·m = 0.737562 lbf·ft. A torque wrench set to 100 N·m tightens to 73.76 lbf·ft.

An honest tool about its conventions

Four choices are stated in black and white: the month is the mean Gregorian month (30.436875 days), Mach is 340.29 m/s (sound at 15 °C at sea level, varies with altitude), the calorie is thermochemical (4.184 J, not the IT calorie at 4.1868 J) and the BTU follows the ISO standard (1,055.05585262 J). Magnetism and heat flux are separated by physical quantity (teslas on one side, webers on the other): never mix apples and oranges. Decibels and DMS get their own calculator, since they are not linear conversions.

Who can benefit?

The traveler converting miles, gallons and Fahrenheit, the cook facing a recipe in ounces and °F, the physics student checking orders of magnitude, the DIYer switching from metric to imperial, the salesperson pricing freight in tons and pounds, and the engineer juggling pascals, newtons and joules. In every case: one value, two units, one verifiable result — in one second, no sign-up.

Length: from the human body to the stars

The inch comes from the width of a thumb: today it is exactly 2.54 cm under the 1959 international agreement between English-speaking countries. The foot (30.48 cm) matched a man's foot, and the yard (0.9144 m, 3 feet) the distance from nose to thumb of an outstretched arm. The mile (1,609.344 m) descends from the Roman thousand paces — a thousand double-steps of 1,480 m, revalued by the British at 8 furlongs. The nautical mile (1,852 m) is more learned: one minute of arc of terrestrial meridian, hence its use in navigation. Beyond that, astronomers count in astronomical units (Earth–Sun distance, 149.6 million km), light-years (9,461 billion km) and parsecs (3.26 light-years, from stellar parallax).

Where do these units come from? A short dictionary

The pound (exactly 453.59237 g) comes from the Roman libra, hence its “lb” symbol. It divides into 16 ounces (28.35 g), the unit of Anglo-Saxon recipes and jewelry. The grain (64.8 mg), the smallest unit of the system, matched the weight of a barley grain. The stone (6.35 kg, 14 pounds) is still used to weigh people in the United Kingdom and Ireland. For freight, beware false twins: the American short ton (907 kg) and the British long ton (1,016 kg) bracket the metric ton (1,000 kg). The metric quintal is exactly 100 kg.

Volume: the gallon headache

The liter is simple: 1 dm³, i.e. 1 kg of water at 4 °C. Everything gets complicated with the gallon: the US gallon (3.785 L, 231 cubic inches) served wine, while the imperial gallon (4.546 L, 10 pounds of water at 62 °F) was imposed by the British Parliament in 1824. Its subdivisions — quart, pint, fluid ounce, tablespoon — inherit the gap. The petroleum barrel (159 L, 42 US gallons) still sets the price of crude. In metric cooking, remember the chain: 1 L = 10 dL = 100 cL = 1,000 mL, and 1 mL = 1 cm³.

Pressure: from weather to tires

The pascal, the SI unit, is one newton per square meter — too small day to day, hence the hectopascal of weather reports (1,013 hPa on average). The bar (100,000 Pa, roughly atmospheric pressure) equips tires and compressors. Psi (pounds per square inch, 6,894.76 Pa) rules overseas: 1 bar = 14.5 psi. The atmosphere (101,325 Pa) recalls Torricelli's experiment, and torr as well as mmHg (133.32 Pa) still measure blood pressure and industrial vacuum.

Speed: knots, Mach and miles

The knot (1.852 km/h) comes from the knotted log line sailors paid out to measure speed — hence “making 20 knots”. Mach relates speed to the speed of sound (340.29 m/s at 15 °C at sea level, varying with altitude and temperature): a plane at Mach 0.85 flies at 85% of that speed. The mile per hour still rules American and British roads: 1 mph = 1.609344 km/h.

Energy and power: calories, BTU and horsepower

The calorie (4.184 J thermochemical) is the energy to heat 1 g of water by 1 °C; the food kilocalorie follows the same definition per kilogram. The BTU (1,055.06 J) is its British cousin, the star of American air conditioning. The kilowatt-hour (3.6 MJ) bills electricity: the power of a 1,000 W heater for one hour. For power, the French cheval-vapeur (735.5 W) comes from a draft horse's effort, while James Watt's horsepower (745.7 W) slightly overstates the same horse — hence 100 ch = 73.55 kW but 100 hp = 74.57 kW.

Force, electricity and radiation

The newton (1 kg·m/s²) honors Newton, and the pound-force (4.44822 N) weighs one pound on Earth — never confuse mass and force. In electricity, volt, ampere, ohm and watt bear the names of Volta, Ampère, Ohm and Watt, 19th-century pioneers; your meter's kilowatt-hour thus pays tribute to two of them. The tesla measures magnetic fields (a fridge magnet is ~5 mT), the becquerel counts disintegrations per second, the gray deposited energy and the sievert its biological hazard — three units not to swap in radiation protection. The mole (6.022 × 10²³ entities) and the decibel (logarithmic scale, +10 dB = 10 times more intensity) round off this tour.