Measurement   US   Customary   Unit   SI Unit   To Convert   Multiply By
  LENGTH   Foot   Meter   Feet to Meters   0.3048
  AREA   Square Foot   Square Meters   Square Feet to Square Meters   0.09290304
  AREA   Square Foot   Hectares   Square Feet to Hectares   0.000009290304
  AREA   Acres   Hectares   Acres to Hectares   0.4046873
  VOLUME   US Fluid Ounce   Milliliters   Fluid Ounces to Milliliters   29.57353
  VOLUME   Gallon   Liters   Gallons to Liters   3.785412
  VOLUME   Gallon   Steres   Gallons to Steres   0.003785412
  VOLUME   Cubic Foot   Steres   Cubic Feet to Steres   0.02831685
  MASS   Pound   Kilogram   Pounds to Kilograms   0.4535924
  VELOCITY   Foot/Second   Meter/Second   Ft / sec to m / s   0.3048
  VELOCITY   Miles/Hour   Meter/Second   mph to m / s   0.44704
  FORCE   Pound   Newton   Pounds to Newtons   4.44822205
  PRESSURE   Pounds per Square Inch   Pascal   psi to Pascals   6,894.757
  ENERGY   Foot Pound   Joule   Foot Pounds to Joules   1.355818
  POWER   Horsepower   Watt   Horsepower to Watts   745.6999
  ANGLE   Degree   Radian   Degrees to Radians   .01745329

If you are wondering what the “SI Unit” is, it means the International System of Units in use by just about every counrty except the United States which has been slow to adopt it.
The seven basic units of the International System of Units (or Système International as it is also called), are ampere (electrical current), kelvin (temperature), second (time), meter (length), kilogram (mass), candela (luminosity) and mole (amount of subtance).
Basically, in everyday life, we don’t use amperes, candelas or moles that much and the Celsius scale is used much more often than Kelvin, which is why those units are not listed in the above table.

The hectare is not a convenient unit for area in everyday life. You could say your kitchen floor measures 0.0008918692 hectares but that doesn’t give you a good idea of its size. A hectare is a rather large unit of measure 100 x 100 meters (10,000 square meters!). The sqaure meter (1 meter by 1 meter) is much more convenient for everyday use. One square foot equals 0.09290304 square meters.

The stere (cubic meter) is another inconvenient unit for everyday life. One cubic meter (1m x 1m x 1m) is a huge amount of volume and it equals 1,000 liters (35.31 cubic feet) and one stere of water weighs 2,200 pounds!
Liters and milliliters are much more convenient even though they are not SI Units.