Resistivity of Metals Chart & Calculator

Resistivity values for common metals, plus resistance and temperature correction, step by step

Find the resistance of 50 m of copper with a 10 mm^2 cross-section

Compare copper and aluminium conductors of the same size over 50 m

Correct a 0.084 ohm copper conductor from 20 C to 75 C

Find the nichrome wire length for a 48 ohm heating element of 0.5 mm diameter

What Electrical Resistance Actually Is

Resistance is how strongly a particular object opposes the flow of charge, defined by

$R = \frac{V}{I} \qquad [\Omega]$

with $V$ in volts and $I$ in amperes. One ohm is one volt per ampere. It is a property of the object — this length of this wire.

Resistivity $\rho$ is the corresponding property of the material, independent of shape, and the two are joined by the geometry:

$R = \frac{\rho L}{A} \qquad \rho = \frac{RA}{L}$

$\rho$ — resistivity, ohm-metres (Ω·m)
$L$ — length, metres (m)
$A$ — cross-sectional area, square metres (m²)

Physically, resistance is the scattering of conduction electrons by lattice vibrations and by impurities. Heating the metal increases the vibrations, which is why metals get more resistive as they warm.

The operating assumption: a uniform, homogeneous conductor at a stated temperature carrying DC.

Resistivity of Metals Chart

Values at 20 °C, with the temperature coefficient $\alpha$ per °C referenced to 20 °C:

Material	$\rho$ (Ω·m)	$\alpha$ (per °C)
Silver	$1.59 \times 10^{-8}$	$0.0038$
Copper	$1.68 \times 10^{-8}$	$0.00393$
Gold	$2.44 \times 10^{-8}$	$0.0034$
Aluminium	$2.65 \times 10^{-8}$	$0.00429$
Tungsten	$5.60 \times 10^{-8}$	$0.0045$
Iron	$9.71 \times 10^{-8}$	$0.0050$
Nichrome	$1.10 \times 10^{-6}$	$0.0004$

Correct to another temperature with the linear relation

$\rho_T = \rho_{20}\left[1 + \alpha (T - 20)\right]$

Nichrome is roughly $65$ times more resistive than copper and barely changes with temperature, which is exactly what a heating element needs.

Treat these as nominal textbook values. Real conductors vary with alloy, temper and purity, and a design that depends on the number should use the supplier's certified data, with any current-carrying decision made under the applicable wiring code.

Common Mistakes to Avoid

Using a resistivity without its temperature — the chart is at 20 °C, and a conductor running hot is measurably more resistive.
Leaving the area in mm² — $10$ mm² is $1 \times 10^{-5}$ m². Skipping this is a factor of a million.
Swapping resistance and resistivity — resistivity is Ω·m and belongs to the material; resistance is Ω and belongs to the object.
Assuming aluminium can simply replace copper — for the same resistance an aluminium conductor needs roughly $58\%$ more cross-sectional area.
Applying the linear $\alpha$ far outside its range — it is a first-order fit valid near the reference temperature, not down to cryogenic or up to melting temperatures.
Forgetting that heating is self-reinforcing — current heats the conductor, which raises resistance, which raises the drop.
Reading nichrome's low $\alpha$ as low resistivity — its resistivity is very high; it is the change with temperature that is small.

Examples

Step 1: Area:

A = 10\ \text{mm}^2 = 1.0 \times 10^{-5}\ \text{m}^2

Step 2: Copper:

R = (1.68 \times 10^{-8}\ \Omega\cdot\text{m})(50\ \text{m}) \div (1.0 \times 10^{-5}\ \text{m}^2) = (8.40 \times 10^{-7}) \div (1.0 \times 10^{-5}) = 0.0840\ \Omega

Step 3: Aluminium:

R = (2.65 \times 10^{-8})(50) \div (1.0 \times 10^{-5}) = (1.325 \times 10^{-6}) \div (1.0 \times 10^{-5}) = 0.1325\ \Omega

Step 4: Ratio:

0.1325 \div 0.0840 = 1.58

, so aluminium is

58\%

more resistive at the same size

Step 5: To match:

A_{\text{Al}} = 10\ \text{mm}^2 \times 1.58 = 15.8\ \text{mm}^2

Answer: Copper

0.0840

Ω, aluminium

0.1325

Ω; about

15.8

mm² of aluminium matches

10

mm² of copper

Step 1: Temperature rise above the reference:

75\ ^\circ\text{C} - 20\ ^\circ\text{C} = 55\ ^\circ\text{C}

Step 2:

\alpha \Delta T = (0.00393\ ^\circ\text{C}^{-1})(55\ ^\circ\text{C}) = 0.2162

Step 3:

R_{75} = R_{20}(1 + 0.2162) = (0.0840\ \Omega)(1.2162)

Step 4:

R_{75} = 0.1022\ \Omega

Step 5: That is a

21.6\%

increase, which is why voltage-drop checks are done at the conductor's operating temperature

Answer:

R_{75} \approx 0.102

Ω, about

22\%

above the 20 °C value

Step 1:

A = \pi d^2/4 = \pi (0.50 \times 10^{-3}\ \text{m})^2/4 = \pi (2.50 \times 10^{-7}\ \text{m}^2)/4 = 1.963 \times 10^{-7}\ \text{m}^2

Step 2: Rearrange:

L = RA/\rho

Step 3:

L = (48\ \Omega)(1.963 \times 10^{-7}\ \text{m}^2) \div (1.10 \times 10^{-6}\ \Omega\cdot\text{m})

Step 4: Numerator:

9.425 \times 10^{-6}\ \Omega\cdot\text{m}^2

, so

L = 8.57\ \text{m}

Step 5: On

240

I = 240\ \text{V} \div 48\ \Omega = 5.0\ \text{A}

Step 6:

P = VI = (240\ \text{V})(5.0\ \text{A}) = 1200\ \text{W}

Answer:

L \approx 8.57

m of wire, drawing

5.0

A and dissipating

1200

W on

240

Frequently Asked Questions

Resistance is the ratio of the voltage across an object to the current through it, R = V/I, measured in ohms. Microscopically it is the scattering of conduction electrons by lattice vibrations and impurities, which is why metals become more resistive as they get hotter.

Resistivity is a material property in ohm-metres and does not depend on shape. Resistance is a property of a specific object in ohms and depends on length and cross-section as well as material, through R = rho L / A.

Silver, at about 1.59 x 10^-8 ohm-metres at 20 C, just below copper at 1.68 x 10^-8. Copper is used almost everywhere instead because it costs far less and does not tarnish into a poorly conducting surface layer.

For metals, use R_T = R_20 [1 + alpha (T - 20)] with alpha in reciprocal degrees Celsius. Copper's alpha of 0.00393 means a conductor at 75 C has about 22% more resistance than at 20 C. The relation is a first-order fit near the reference temperature.

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Resistivity of Metals Chart & Calculator

Resistivity values for common metals, plus resistance and temperature correction, step by step

What Electrical Resistance Actually Is

Resistivity of Metals Chart

Common Mistakes to Avoid

Examples

Frequently Asked Questions

What is electrical resistance in physics?

What is the difference between resistance and resistivity?

Which metal has the lowest resistivity?

How does temperature change resistance?

Try AI-Math for Free

Resistivity of Metals Chart & Calculator

Resistivity values for common metals, plus resistance and temperature correction, step by step

What Electrical Resistance Actually Is

Resistivity of Metals Chart

Common Mistakes to Avoid

Examples

Problem: TheThe The0.0840\ \Omegacopperconductoraboverunsatcopper conductor above runs atcopperconductoraboverunsat75°C.Correctitsresistance,taking°C. Correct its resistance, taking°C.Correctitsresistance,taking\alpha = 0.00393per°Cfrom20°C. per °C from 20 °C.per°Cfrom20°C.

Problem: HowlongmustanichromewireofHow long must a nichrome wire of Howlongmustanichromewireof0.50mmdiameterbetogivemm diameter be to givemmdiameterbetogive48\ \Omega?Take? Take ?Take\rho = 1.10 \times 10^{-6}Ω⋅m,thenfindthepoweronΩ·m, then find the power onΩ⋅m,thenfindthepoweron240V. V.V.

Frequently Asked Questions

What is electrical resistance in physics?

What is electrical resistance in physics?

What is the difference between resistance and resistivity?

What is the difference between resistance and resistivity?

Which metal has the lowest resistivity?

Which metal has the lowest resistivity?

How does temperature change resistance?

How does temperature change resistance?

Try AI-Math for Free