The siemens (symbol: S) is an SI derived unit of measurement for electric conductance, being the inverse of the ohm (Ω), named after Werner von Siemens.

S = A / V

• S = Siemens
• A = Amperes
• V = Volts

• The forumla for computing conductance is as follows:

G = 1 / R = S

• G = Conductance
• R = Resistance (Ω)
• S = Siemens

Example: G = 1 / 6 Ω = 0.1667 S

Mho is a now eccentric name for this unit of electrical conductance, equal to 1 Ω⁻¹. It is derived by spelling ohm backwards. Its symbol is (the upside-down letter Ω). The term siemens is used universally in science and primarily in electrical applications, while mho is used primarily in electronic applications.

SI electricity units