Search electrical resistivity and conductivity reference values for metals and engineering alloys by grade, designation or material family.
Electrical resistivity is a fundamental material property describing how strongly a substance opposes electric current. It is commonly represented by the Greek letter rho (ρ) and expressed in ohm-metres (Ω·m).
Electrical conductivity is the reciprocal of resistivity. A material with low resistivity has high electrical conductivity and generally allows current to pass more easily. Copper and silver therefore have much higher conductivity than stainless steel, titanium and most carbon steels.
For a uniform conductor, resistance also depends on its geometry. The relationship is R = ρL/A, where R is resistance, ρ is resistivity, L is conductor length and A is cross-sectional area. Consequently, two wires made from the same metal can have very different electrical resistance if their dimensions differ.
| Material | Resistivity at ~20°C | Conductivity | Relative Electrical Behavior |
|---|---|---|---|
| Silver | ~1.59 × 10⁻⁸ Ω·m | ~62.9 MS/m | Very high conductivity |
| Copper | ~1.68 × 10⁻⁸ Ω·m | ~59.6 MS/m | Very high conductivity |
| Aluminum | ~2.65 × 10⁻⁸ Ω·m | ~37.7 MS/m | High conductivity |
| Gold | ~2.44 × 10⁻⁸ Ω·m | ~41.0 MS/m | High conductivity |
| Brass C360 | ~6.2 × 10⁻⁸ Ω·m | ~16 MS/m | Moderate conductivity |
| Carbon Steel | ~1.5 × 10⁻⁷ Ω·m* | ~6.7 MS/m* | Much higher resistance than copper |
| Stainless Steel 304 | ~7.2 × 10⁻⁷ Ω·m | ~1.4 MS/m | Low conductivity |
| Titanium Grade 5 | ~1.7 × 10⁻⁶ Ω·m | ~0.59 MS/m | Very low conductivity |
| Factor | Effect on Resistivity | Why It Matters |
|---|---|---|
| Temperature | Usually increases in pure metals | Hot conductors have higher resistance than the same conductors at room temperature. |
| Alloying | Can increase resistivity substantially | Alloying disrupts the metal's crystal lattice and changes electron scattering. |
| Purity | Impurities generally increase resistivity | High-purity copper and other conductors can achieve lower resistivity. |
| Cold working | Can change resistivity slightly | Defects introduced by deformation affect electron scattering. |
| Heat treatment | May alter resistivity | Precipitation, phase changes and microstructure can affect electrical behavior. |
| Temperature range | Can change the relationship between temperature and resistance | Electrical calculations over wide temperature ranges require temperature-dependent data. |
Resistivity and conductivity describe the same underlying electrical behavior from opposite directions. Resistivity measures how strongly the material resists current, while conductivity measures how readily it conducts current.
The relationship is:
σ = 1 / ρ
where σ is electrical conductivity in siemens per metre (S/m) and ρ is electrical resistivity in ohm-metres (Ω·m).
For example, copper has very low resistivity and therefore very high conductivity. Stainless steel has considerably higher resistivity and consequently much lower electrical conductivity.
For a uniform conductor, resistance can be estimated from its material resistivity and physical dimensions:
R = ρL / A
| Variable | Meaning | SI Unit |
|---|---|---|
| R | Electrical resistance | Ohm (Ω) |
| ρ | Electrical resistivity | Ohm-metre (Ω·m) |
| L | Conductor length | Metre (m) |
| A | Cross-sectional area | Square metre (m²) |
This means that increasing conductor length increases resistance, while increasing cross-sectional area decreases resistance. Material selection is another major factor because metals with lower resistivity produce lower resistance for the same dimensions.
| Material | Approx. Conductivity | Typical Electrical Use |
|---|---|---|
| Silver | ~62.9 MS/m | Specialized contacts and high-performance electrical applications |
| Copper | ~59.6 MS/m | Wiring, busbars, motor windings and electrical conductors |
| Aluminum | ~37.7 MS/m | Power transmission and lightweight conductors |
| Gold | ~41 MS/m | Electrical contacts and corrosion-resistant connections |
| Brass | Typically much lower than copper | Terminals, connectors and electrical hardware |
| Carbon Steel | Several MS/m, grade dependent | Structural and electromagnetic applications rather than primary conductors |
| Stainless Steel | Generally around 1–2 MS/m for common grades | Resistive heating, structural electrical components and specialized conductors |
| Titanium | Typically below 1 MS/m | Applications where corrosion resistance and strength matter more than conductivity |
What is electrical resistivity? Electrical resistivity is a material property that measures opposition to electric current. Its SI unit is the ohm-metre (Ω·m).
What is the difference between resistivity and resistance? Resistivity is an intrinsic material property, while resistance depends on both the material and the conductor's geometry. Resistance is calculated from resistivity, length and cross-sectional area.
Which metal has the lowest electrical resistivity? Silver has extremely low resistivity among metals, followed closely by copper. Copper is used far more extensively for electrical conductors because it provides excellent conductivity at a more practical cost.
Why is copper used for electrical wiring? Copper combines very high electrical conductivity with good ductility, manufacturability and corrosion resistance. It can carry substantial current using relatively compact conductor sizes.
Is aluminum a good electrical conductor? Yes. Aluminum has substantially higher resistivity than copper but remains a good conductor and has a much lower density. It is widely used for electrical transmission and other applications where low weight is important.
Is stainless steel electrically conductive? Yes, but its electrical conductivity is much lower than copper or aluminum. Common stainless steels have relatively high electrical resistivity.
Does temperature affect electrical resistivity? Yes. The resistivity of most pure metals increases as temperature rises. This means a metal conductor normally has greater electrical resistance when hot.
Does alloying increase resistivity? Generally, alloying increases electrical resistivity compared with the corresponding pure metal. The exact effect depends on the alloying elements and concentration.
What is IACS? IACS stands for International Annealed Copper Standard. Electrical conductivity expressed as a percentage of IACS compares a material's conductivity with the reference conductivity assigned to annealed copper.
Can these values be used for precision electrical design? They are reference values for material comparison. Precision design should use the manufacturer's certified material data at the actual operating temperature, material condition and applicable standard.