Metrication in the United States There are no U.S. customary units for electric current, potential difference, or charge since these concepts were developed after the international adoption of metric in science. The metric units ampere, volt, ohm and coulomb are the only units used. The SI term hertz has replaced the term "cycles per second" as a unit of frequency. Energy is often measured in watt hours, BTUs, therms or calories rather than the SI joule. Residential and commercial electrical energy use is metered and billed in kilowatt hours, kW·h, as in most metric countries. Force measurements regularly use the pound instead of the SI
Gram per cubic centimetre Gram per cubic centimetre Gram per cubic centimetre is a unit of density in the CGS system, commonly used in chemistry, defined as mass in grams divided by volume in cubic centimetres. The official SI symbols are g/cm, g·cm, or g cm. It is equivalent to the units gram per millilitre (g/mL) and kilogram per litre (kg/L). The density of water is about 1 g/cm, since the gram was originally defined as the mass of one cubic centimetre of water at its maximum density at 4 °C. 1 g/cm is equivalent to: 1 kg/m = 0.001 g/cm(exactly) 1 lb/ft ≈