Convert:

A small freeware (free of charge software, even for commercial use) that can be installed on your computer.

Online converter to convert almost everything:

Length, Temperature, Speed, Volume, Weight, Cooking, Area, Fuel Economy, Currency.

Acceleration Many different acceleration constants. g-unit, meter/square second, more...

Angles Gradients, Radians, Degrees, Minutes, Seconds, Points, More...

Area Square centimeter, Square meter, Square inch, Square foot, Square mile, Square Kilometer, Acres, Circles, More...

Astronomical Astronomical unit, light-years, parsecs, More...

Clothing Convert clothing sizes between many different countries.

Computers and Electronics Various conversions and calculators related to computers and electronics.

Cooking Various cooking volume conversions, including Drop, Dash, Pinch, Teaspoons, Tablespoons, Cups, etc. Plus other cooking conversions such as butter weight, and gas mark temperatures.

Date/Time Several different converters and calculators related to dates and times.

Density kg/cubic meter, lbm/cubic foot, lbm/gallon, aluminum, copper, gold, water, More...

Energy Joules, Btu, calories, electronvolt, erg, watt hour, therm, toe, tce, More...

Finance Several calculators and conversions related to finance

Flow Rate Many different flowrate conversions. Includes separate pages for mass based, volume based, and mole based flowrates.

Force Dyne, gram-force, poundals, newtons, pounds, kgm-force, More...

Frequency Hertz, cycles per second, revolutions per second, degrees per second, radians per second, many more...

Fun Stuff Several fun and interesting calculators and conversions

Length/Distance Millimeters, Centimeters, Inches, Feet, Yards, Meters, Kilometers, Miles, Mils, Rods, Fathoms, Nautical Miles, More...

Light Conversion calculators for illuminance and luminance.

Miscellaneous Several calculators and conversions that didn't fit any other category

Numbers Number conversions and information. Base conversion, SI Standard prefixes, American and British naming conventions, and more...

Power Watts, BTU/hour, foot-lbs/second, Horsepower, kilowatts, More...

Pressure dyne/sq cm, Pascal, poundal/sq foot, Torr, inch H2O, inch mercury, More...

Speed centimeters/second, meters/second, kilometers/hour, feet/second, feet/minute, miles/hour, knots, mach, More...

Temperature Celsius, Fahrenheit, Rankine, Reaumur, and Kelvin

Torque Pound-force Foot, Pound-force Inch, Kilogram-force Meter, and Newton meter

Viscosity Poise, Centipoise, Water, Oil, Glycerin, more...

Volume Liquid and Dry. Liters, Fluid Ounces, Pints, Quarts, Gallons, Milliliter/cc, Barrels, Gill, Hogshead, More...

Weight/Mass Kilograms, Ounces, Pounds, Troy Pounds, Stones, Tons, More...