Estimate voltage drop in a 12V, 24V or 48V DC circuit using copper or aluminium wire and round-trip conductor length.
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DC circuit parameters
Enter one-way cable distance; the calculator includes outgoing and return conductors.
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How does it work?
For a two-wire DC circuit: R = 2 × one-way distance × resistivity / cross-section. Voltage drop ΔV = current × R and cable loss P = current² × R.
At 20°C, approximate resistivities are 0.0175 Ω·mm²/m for copper and 0.028 Ω·mm²/m for aluminium. Resistance increases with temperature.
Important: This calculator does NOT select a safe cable size, fuse or breaker. It does not cover current carrying capacity, insulation, installation method or connector losses. Use appropriate wiring codes and manufacturer guidance.
Frequently asked questions
Why multiply cable length by two?
Current travels to the load and returns by a second conductor. Both paths contribute to resistance.
Does less than 3% mean code compliant?
No. The display threshold is only a design heuristic. Applicable limits depend on the system and local regulations.
USEFUL FOR THIS ESTIMATE
Useful equipment for this calculation
Practical buying criteria — no invented offers or prices.
02 SUGGESTIONS
🧵WIRING
Copper DC cable
Compare cross-section, conductor material, insulation and installation requirements.
✓ What to check
📟MEASUREMENT
Digital multimeter
Check voltage/current ranges, safety rating and supplied probes.
✓ What to check
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Worked example: 24 V DC voltage drop
Examples explain the formulas and do not represent current retail prices.
2.5 mm² cable, 8 m, 10 A
At 20°C the copper loop resistance is approximately 0.112 Ω. At 10 A the voltage drop is around 1.12 V (4.67% of 24 V), with 11.2 W of cable losses.
How to reduce losses
Increase conductor cross-section, shorten the run or reduce load current. The result does not determine safe ampacity or protection.
