Electrical tool
CCS DC resistance calculator
Compute DC resistance for any CCS grade and diameter from the IACS definition (IEC 60028: 100% IACS = 0.017241 Ω·mm²/m at 20 °C), then check a planned run against its resistance budget.
Anchors: IEC 60028 (0.017241 Ω·mm²/m = 100% IACS at 20 °C); grade conductivities 21/30/40/55% IACS; wire range 0.10-4.00 mm. Every output is the anchor divided by cross-section.
Result
Ω / m
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Run total (Ω)
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Resistivity (Ω·mm²/m)
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| Diameter | 21% (Ω/m) | 30% (Ω/m) | 40% (Ω/m) | 55% (Ω/m) |
|---|---|---|---|---|
| 0.10 mm | 10.45 | 7.32 | 5.49 | 3.99 |
| 0.20 mm | 2.61 | 1.83 | 1.37 | 0.998 |
| 0.30 mm | 1.16 | 0.813 | 0.610 | 0.443 |
| 0.50 mm | 0.418 | 0.293 | 0.220 | 0.160 |
| 1.00 mm | 0.105 | 0.073 | 0.055 | 0.040 |
| 2.00 mm | 0.026 | 0.018 | 0.014 | 0.0100 |
| 3.00 mm | 0.012 | 0.0081 | 0.0061 | 0.0044 |
| 4.00 mm | 0.0065 | 0.0046 | 0.0034 | 0.0025 |
Reference grid at 20 °C, one-way. Values derive from the IACS anchor. Your lot's measured resistance on the MTC governs.
Frequently Asked Questions (FAQ)
Where does the resistance formula come from?
Straight from the International Annealed Copper Standard itself (IEC 60028): 100% IACS is defined as 0.017241 Ω·mm²/m at 20 °C. A CCS grade quoted at N% IACS therefore has a resistivity of 0.017241/N Ω·mm²/m, and one division by cross-section later you have resistance per metre. The tool is that arithmetic. Nothing more.
How close is the computed figure to a measured one?
The derivation is exact for whatever composite conductivity you feed it. The conductivity itself is the measured quantity, and both ASTM B227 (hard-drawn) and ASTM B910/B910M (annealed) write electrical resistance into their conformance requirements. So the MTC of the lot you buy is the authority. Use this tool for sizing and comparison, never as a certificate.
Does temperature change the result?
Yes, and it adds up over long runs. The IACS anchor and every figure here are at 20 °C, while copper's resistivity climbs roughly 0.4% per °C. A 40 °C rise therefore puts a hot conductor about 16% above the table value. For grounding and signal-budget work, 20 °C stays the conventional starting point.
Why does the tool ask how many legs the circuit has?
A return circuit carries the current out and back, so both legs add series resistance. Pick 2 legs and the tool doubles the one-way figure. Grounding runs are usually 1-leg paths to earth. Harness and signal loops are 2-leg circuits.
Which diameters are real stock?
Single-end CCS wire runs 0.10-4.00 mm with tolerance ±0.003 to ±0.020 mm. Anything inside that band computes here. Outside it, ask us: the formula still holds, but the draw may not exist.
Need the lot behind the number?
Send the grade, diameter and run length. We quote against stock CCS with a heat-number-traceable MTC that carries the measured resistance.