Units in Common Use in the English and SI System

Some units that are commonly used in both the English system and the International System of Units (SI) are:

• Length: inch (in) and meter (m)
• Mass: pound (lb) and kilogram (kg)
• Time: second (s)
• Temperature: degree Fahrenheit (°F) and degree Celsius (°C)
• Energy: British Thermal Unit (BTU) and Joule (J)
• Force: pound-force (lbf) and Newton (N)
• Pressure: pound-force per square inch (psi) and Pascal (Pa)
• Power: horsepower (hp) and Watt (W)
• Electric current: ampere (A)
• Voltage: Volt (V)
• Electric charge: Coulomb (C)
• Frequency: Hertz (Hz)
• Electric capacitance: Farad (F)
• Electric resistance: Ohm (Ω)
• Magnetic field strength: Oersted (Oe) and Ampere-turns per meter (A/m)

It's important to note that while these units may be used in both systems, they may have different definitions or conversions between the systems. For example, one pound is equal to approximately 0.4536 kilograms, and one inch is equal to approximately 2.54 centimeters. It's always important to double-check unit conversions and ensure that units are used consistently throughout any calculations or measurements.

Table 1. Gives a list of some commonly used units in the English and SI systems, conversion between units, and also their relation to the base units. The lb is used as both the unit of mass and the unit of force.

Tabla 2. Gives a list of the base units used in instrumentation and measurement in the English and SI systems and also the conversion factors, other units are derived from these base units.