Convert electrical resistivity between ohm-metre, ohm-centimetre and microhm units.
Electricity • 6 units
All 6 units on the Electric Resistivity Converter are defined against the Ohm-meter (Ω·m), 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 Ω·m = 100 Ω·cm. Change either side and every row in the table recalculates with it.
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The page's default step, ohm-metres to ohm-centimetres, multiplies by 100, and the more useful derived quantity follows from dividing rather than multiplying. Resistivity divided by thickness gives sheet resistance, expressed in ohms per square, which is how thin films and printed conductors are actually specified. Standard one-ounce circuit-board copper is about 35 µm thick, so at copper's 1.68 × 10⁻⁸ Ω·m it works out to roughly 0.48 milliohms per square — a figure that lets a designer estimate track resistance by counting squares along the track rather than measuring anything.
Semiconductors are where the range of this table earns its width. Silicon can be doped across roughly eight orders of magnitude of resistivity, from milliohm-centimetres in heavily doped substrate material to hundreds of ohm-centimetres in high-resistivity float-zone wafers, and wafers are bought and sold on that number because it maps directly onto dopant concentration. The measurement is normally made with a four-point probe, which passes current through the outer pair of contacts and reads voltage on the inner pair, precisely so that contact resistance never enters the result.
Two conventions catch people converting metal resistivities. The first is the IACS scale, which fixes 100% conductivity as 1.7241 µΩ·cm at 20 °C for annealed copper — hard-drawn copper sits near 97%, and aluminium alloys are quoted as a percentage of it rather than in SI units at all. The second is temperature: pure metals rise in resistivity with heat, which is why precision shunts and standard resistors are wound from manganin or constantan, alloys chosen because their resistivity barely moves over a working temperature range. A resistivity quoted without its reference temperature is an incomplete figure.
Quick reference — 1 Ohm-meter (Ω·m) is equal to:
| Ohm-centimeter | Ω·cm | 100 |
| Ohm-inch | Ω·in | 39.370079 |
| Microhm-centimeter | µΩ·cm | 100,000,000 |
| Microhm-meter | µΩ·m | 1,000,000 |
| Nanohm-meter | nΩ·m | 1,000,000,000 |
6 units of electric resistivity, each a fixed multiple of the Ω·m. The table spans 1,000,000,000:1, from nΩ·m (0.000000001 Ω·m) to Ω·m (1 Ω·m). 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 Ω·m = 1 Ω·m1 Ω·cm = 0.01 Ω·m1 Ω·in = 0.0254 Ω·m1 µΩ·cm = 0.00000001 Ω·m1 µΩ·m = 0.000001 Ω·m1 nΩ·m = 0.000000001 Ω·mwhere:
Assumptions: Factors are exact definitions. Full double precision is carried internally and rounding is applied only for display.
Result25 Ω·m = 2500 Ω·cm
Resistance depends on shape; resistivity does not. Measured in ohm-metres (Ω·m), it is the property of the substance itself, so a copper wire and a copper busbar share one resistivity even though their resistances differ by orders of magnitude. Annealed copper sits at about 1.68 × 10⁻⁸ Ω·m, aluminium near 2.65 × 10⁻⁸, and the difference is exactly why aluminium conductors must be physically fatter to carry the same current.
The unit conversions here are unusually treacherous because the older units are not decimal siblings. One ohm-metre equals 10⁸ microhm-centimetres, and cable datasheets frequently quote ohm-circular-mil-per-foot, a unit that folds an area convention into the number itself. Reading a resistivity figure without checking its unit is how conductor-sizing errors begin.