Convert electrical conductance between siemens, millisiemens, microsiemens and mho.
Electricity • 5 units
All 5 units on the Electric Conductance Converter are defined against the Siemens (S), so each result is one conversion factor away from a single reference rather than the end of a chain of roundings.
The conversion this page is most often opened for is ready before you type anything: 1 S = 1,000 mS. Change either side and every row in the table recalculates with it.
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The page opens on siemens to millisiemens, a plain factor of a thousand, but the skill worth having is moving between conductance and resistance in your head. The reciprocal of 1 S is 1 Ω; of 1 mS, 1 kΩ; of 1 µS, 1 MΩ. That inverse symmetry means the prefixes run backwards relative to resistance, so a material described as more conductive carries a smaller-sounding prefix in siemens and a larger one in ohms. Reading a datasheet that mixes the two without noticing the flip is the standard route to an answer a million times out.
Conductance is also the natural unit for anything measured as a leak rather than as a path. Insulation resistance in the hundreds of megohms is more conveniently written as a few nanosiemens, and the sub-threshold leakage of a transistor is described the same way. In semiconductor work the term reappears as transconductance, in siemens, relating a change in output current to a change in input voltage — historically quoted in mhos, and in vacuum-tube data in micromhos, which is the same unit under a name SI retired in 1971.
Because the mho and the siemens are numerically identical, converting between them takes no arithmetic at all — a rare case where an obsolete unit needs only relabelling. That makes the older term harmless where it is written out plainly and quietly hazardous where it is abbreviated. An inverted omega standing for the mho (℧) still appears on surplus instruments and in scanned manuals, and it reads easily as an ordinary ohm symbol, turning a conductance figure into a resistance one with nothing on the page to signal that anything has gone wrong.
Quick reference — 1 Siemens (S) is equal to:
| Millisiemens | mS | 1,000 |
| Microsiemens | µS | 1,000,000 |
| Kilosiemens | kS | 0.001 |
| Mho | ℧ | 1 |
5 units of electric conductance, each a fixed multiple of the S. The table spans 1,000,000,000:1, from µS (0.000001 S) to kS (1000 S). Conversion is one multiplication into the base unit and one division out of it, with no lookup table and no approximation.
value_to = value_from × (factor_from ÷ factor_to)1 S = 1 S1 mS = 0.001 S1 µS = 0.000001 S1 kS = 1000 S1 ℧ = 1 Swhere:
Assumptions: Factors are exact definitions. Full double precision is carried internally and rounding is applied only for display.
Result25 S = 25000 mS
Conductance is the reciprocal of resistance, measured in siemens (S), where one siemens is one ampere per volt. The older name for the same unit was the mho — ohm spelled backwards — and it is still seen on instruments built before the 1970s.
Working in conductance rather than resistance is not a stylistic choice; it changes which arithmetic is easy. Resistors in parallel simply add their conductances, so three 100 Ω resistors in parallel are 0.01 + 0.01 + 0.01 = 0.03 S, which is 33.3 Ω. The same calculation in ohms requires reciprocals at both ends. That is why conductance dominates in semiconductor and electrochemistry work, where parallel paths are the normal case.