Calculate nichrome wire resistance, length or diameter using typical NiCr 80 or 60 resistivity, plus ohms per meter and AWG coil length and power.

Typical manufacturer values at 20 °C; hot wire reads a few % higher. Choose Custom to enter your own.

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Nichrome Resistance Formula

The following formula is used to calculate the resistance of a nichrome wire.

R = p×L / A
  • Where R is the resistance (ohms)
  • p is the resistivity at the wire temperature (ohm-meters); the example assumes 150 × 10-8 Ω·m
  • L is the length of the wire (m)
  • A is the cross-sectional area of the wire (m2)

To calculate the resistance of a nichrome wire, multiply the resistivity by the length, then divide by the cross-sectional area of the wire.

What is the resistance of nichrome?

Definition:

Nichrome resistivity depends on alloy and temperature. For example, the manufacturer’s Nikrothal 80 and 60 data give approximately 1.09 × 10-6 and 1.11 × 10-6 Ω·m at 20 °C. Wire resistance also depends on its length and cross-sectional area.

How to calculate nichrome resistance?

Example Problem:

The following example outlines how to calculate the resistance of a nichrome wire.

First, use resistivity for the actual alloy and temperature. This example assumes 150 × 10-8 ohm-meters for illustration.

Next, determine the length of the wire. This wire is 100 m long.

Next, determine the cross-sectional area of the wire. Given a diameter of the wire of .025 m, the cross-sectional area can be calculated with the formula:

πD²/4 = π × .025²/4 ≈ .000490874 m²

Finally, calculate the total resistance using the formula above:

R = p*L / A

R = (150 × 10-8) × 100 / (π × .025²/4)

R ≈ .305577 ohms (about .306 ohms)