DC Wire Size Calculator: AWG Gauge, Voltage Drop and Power Loss

Your details

Nominal system voltage, e.g. 12 V, 24 V, 48 V, 120 V.
V
Use peak or maximum continuous load current for worst-case sizing.
A
One-way distance from power source to load. The calculator doubles this for the return path.
ft
NEC recommends 3% max for branch circuits, 5% total. Sensitive electronics often need 2% or less.
%
The maximum operating temperature of the wire insulation. Most standard wiring is rated 75 deg C.
degC
Recommended wire gaugeGood (NEC recommended)
8 AWG

Smallest standard AWG size that keeps voltage drop within your limit

Actual voltage drop0.305V
Voltage drop (%)2.55%
Power loss in wire6.11W
Wire cross-sectional area8.37mm²
Wire diameter3.26mm
Total circuit resistance0.0153Ohm
Required area (m²)0.0000071006
AWG index9
Resistivity0.000000020966
Length (m)3.048
Max ampacity50
2.55 %
Excellent<2Good (NEC)2-3Acceptable3-5High5+

Use 8 AWG for this DC circuit run.

  • Your actual voltage drop is 0.305 V (2.55%), which is good - within the NEC 3% recommendation for branch circuits.
  • The wire will dissipate 6.11 W as heat. Keep runs in ventilated conduit or cable trays when power loss is above a few watts.
  • The ampacity of 8 AWG at 75 deg C is 50 A, which safely covers your 20 A load with margin.
  • Always confirm the final gauge against local electrical codes and the insulation temperature rating of the specific wire product you buy.

Next stepIf the power loss or drop is still too high, try doubling the conductor (running two wires in parallel) or raising the system voltage - 24 V or 48 V systems need far less copper for the same power.

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