Crimp joint resistance calculator

Work out the resistance of a crimp joint and how hot it runs: enter the wire gauge, current and joint quality, and read the milliohms and temperature rise.

Wire, joint & current

Wire gauge

Bare copper conductor at 20 °C

Joint quality

Joint resistance as a share of the bare conductor

Current I

Current through the joint, in A

Ambient temperature

Surrounding air temperature, in °C

Crimp zone length

Crimp barrel length, in mm (≈ 15 mm typical)

Thermal resistance Rth

Joint-to-ambient, typical 100–400 °C/W for a small crimp

Joint resistance & heat

Joint resistance: 0.4725mΩ
Power loss (I²R): 11.81mW
Temperature rise ΔT: 2.36°C
Joint temperature: 27.36°C

A good crimp adds less than 20% to the resistance of the bare conductor — Average (+50%) adds 50% here.

Why crimp quality matters

A poor crimp — air voids, wrong barrel height, or a wire not fully seated in the barrel — can add up to 10× the resistance of a good joint and run noticeably hot. The mechanical penalty is just as real: a 0.05 mm error in crimp height can cut pull-out strength by around 20%.

Pick the parts

Browse related parts:

crimp terminals crimping tools contacts / sockets

Frequently asked questions

How do you calculate the resistance of a crimp joint?

The crimp zone is modelled as a short conductor: base resistance = R per metre × crimp length, scaled by the joint quality. Good joints add 20%, average 50% and poor 100% of the bare conductor resistance. For an 18 AWG wire (0.021 Ω/m at 20 °C) with a 15 mm crimp, that is about 0.315 mΩ before the quality factor.

Why does crimp quality change the resistance so much?

A poor crimp — air voids, wrong barrel height or a wire not fully seated — can add up to 10× the resistance of a good joint. The calculator uses quality factors of 0.2, 0.5 and 1.0 on the bare conductor resistance, and the joint then heats up with ΔT = P × Rth where P = I² × R.

What is a typical thermal resistance for a crimp joint?

A small crimp typically sits between 100 and 400 °C/W, and the calculator defaults to Rth = 200 °C/W. With a 5 A current and an average-quality 18 AWG joint, the rise works out to a few degrees — it is above roughly 30 °C that the tool warns you to check crimp height and tooling.

How it works

IC Source Direct models the crimp zone as a short conductor: R = R_per_m × length, scaled up by the joint quality (good 20%, average 50%, poor 100% of the bare conductor resistance). The joint dissipates P = I² × R and heats up with ΔT = P × Rth to ambient. Values are for bare copper at 20 °C — a DC model, so skin effect is ignored.

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IC Source Direct provides this tool for reference only.

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