Unit Converter

Free online unit conversion calculators for weight, length, temperature, volume, speed, and area. Each converter includes the exact formula, a reference table, and real-world context so the numbers actually mean something.

⚖️ Weight

Convert kilograms, pounds, grams, ounces, and more. Essential for cooking, shipping, and fitness.

Kilograms → Poundskg → lbs Pounds → Kilogramslbs → kg Ounces → Gramsoz → g Grams → Ouncesg → oz Stones → Kilogramsst → kg Kilograms → Stoneskg → st Pounds → Ounceslbs → oz Ounces → Poundsoz → lbs Kilograms → Gramskg → g Grams → Kilogramsg → kg Metric Tons → Kilogramst → kg Kilograms → Metric Tonskg → t

📏 Length

Convert meters, feet, inches, miles, and kilometers. Covers everything from screen sizes to road distances.

Centimeters → Inchescm → in Inches → Centimetersin → cm Meters → Feetm → ft Feet → Metersft → m Kilometers → Mileskm → mi Miles → Kilometersmi → km Millimeters → Inchesmm → in Inches → Millimetersin → mm Yards → Metersyd → m Meters → Yardsm → yd Feet → Inchesft → in Inches → Feetin → ft Miles → Feetmi → ft Nautical Miles → Kilometersnmi → km

🌡️ Temperature

Convert Fahrenheit, Celsius, and Kelvin. Indispensable for cooking, travel, and science.

Celsius → Fahrenheit°C → °F Fahrenheit → Celsius°F → °C Kelvin → CelsiusK → °C Celsius → Kelvin°C → K

🧪 Volume

Convert liters, gallons, cups, fluid ounces, and milliliters. Covers cooking, chemistry, and fuel.

Liters → US GallonsL → gal US Gallons → Litersgal → L Milliliters → US CupsmL → cups US Cups → Milliliterscups → mL Tablespoons → Milliliterstbsp → mL Teaspoons → Milliliterstsp → mL Fluid Ounces → Millilitersfl oz → mL Liters → MillilitersL → mL Milliliters → LitersmL → L US Gallons → Quartsgal → qt Quarts → US Gallonsqt → gal US Cups → Tablespoonscups → tbsp Tablespoons → Teaspoonstbsp → tsp Pints → US Cupspt → cups Liters → PintsL → pt

🏎️ Speed

Convert mph, km/h, knots, and m/s. Covers driving, aviation, and sports.

Miles per Hour → Kilometers per Hourmph → km/h Kilometers per Hour → Miles per Hourkm/h → mph Kilometers per Hour → Meters per Secondkm/h → m/s Meters per Second → Kilometers per Hourm/s → km/h Miles per Hour → Feet per Secondmph → ft/s Knots → Miles per Hourkn → mph

📐 Area

Convert square feet, square meters, acres, and hectares. Covers real estate, agriculture, and construction.

Square Feet → Square Meterssq ft → m² Square Meters → Square Feetm² → sq ft Acres → Hectaresac → ha Hectares → Acresha → ac Square Kilometers → Square Mileskm² → mi² Square Miles → Square Kilometersmi² → km² Square Feet → Acressq ft → ac Square Yards → Square Meterssq yd → m²

Why unit conversions matter

The world uses two major measurement systems: the metric system (used by most countries and all of science) and the US customary system (used primarily in the United States for everyday life). Navigating between these systems is a daily reality for millions of people — whether you're cooking with a European recipe, buying a car with specs in km/h, comparing real estate listings abroad, or following a medication dosage.

Getting conversions wrong has real consequences. A recipe that calls for 200°C (392°F) is ruined if you set the oven to 200°F. A package that weighs 5 kg will be rejected if you fill out a customs form declaring 5 lbs. Knowing the exact conversion — and understanding why it matters — prevents those errors.

Each converter on this page shows the exact mathematical formula alongside an interactive calculator and a reference table. The reference tables let you scan common values at a glance without doing any math. The guide sections explain where and why each measurement system is used, so you build real intuition rather than just copying numbers.

All conversions are based on internationally defined exact values where they exist (such as the exact definition of 1 inch = 2.54 cm), or the best available scientific constants for the rest.

Common questions

Which countries use the metric system?▾

All countries except the United States, Liberia, and Myanmar officially use the metric system. The US uses metric in science, medicine, and military contexts, but US customary units dominate everyday life. The UK officially uses metric but retains miles for road signs and pints for draught beer.

How accurate are these conversions?▾

All conversions use exact or scientifically precise values. For example, 1 inch = 2.54 cm exactly (an internationally defined standard). Temperature conversions use the exact formulas defined by international standards bodies. Rounding only occurs in the display, not in the calculation.

What is the easiest way to convert Celsius to Fahrenheit quickly?▾

Double the Celsius temperature and add 30 for a fast estimate. Example: 20°C → 40 + 30 = 70°F (actual: 68°F). For a more accurate result, multiply by 1.8 and add 32.