24V Wire Size Calculator — DC Gauge & Voltage Drop
Enter the load current, one-way wire length, and maximum acceptable voltage drop. The calculator finds the thinnest AWG copper wire that keeps the voltage drop within your limit for a 24 V DC system.
A
ft
Length unit
%
- 1
Allowable voltage drop
3 % × 24 V ÷ 100 = 0.72 V - 2
Required circular mils
2 × 10.75 × 20 × 15 ÷ 0.72 = 8,958The smallest AWG gauge whose CM ≥ this value is the minimum safe wire size.
How does this calculator work?
For a 24 V DC system, required circular mils = 21.5 × I × L_ft / (0.03 × 24) when targeting 3 % drop (0.72 V). Compared to 12 V, the same load current over the same distance produces half the absolute voltage drop, so you can often use a gauge two sizes thinner than you would at 12 V.
Formula
How this is calculated
A 24 V DC system is commonly used in heavy trucks, larger solar/off-grid installations, industrial equipment, and telecommunications. Because voltage is double that of a 12 V system, the same load draws half the current, which means the wire can be one quarter the cross-sectional area for the same voltage-drop percentage and wire length (since power loss scales with I²). This makes 24 V the preferred choice for long cable runs.
The calculation uses the industry-standard circular-mils formula: required CM = 2 × 10.75 × I × L_ft / V_drop. Here, 10.75 Ω·CM/ft is the copper resistivity constant, 2× accounts for the round-trip current path, and V_drop is the absolute voltage drop limit (e.g. 3 % of 24 V = 0.72 V). The smallest AWG gauge whose tabulated CM value meets or exceeds the requirement is the recommended minimum size.
Always cross-check against the gauge's ampacity rating (shown in the results) to ensure the wire does not overheat under continuous load. Derating for conduit fill, high ambient temperature, or continuous-duty loads (multiply the rating by 0.8 for continuous loads) may require stepping up one gauge beyond the voltage-drop minimum.
Frequently asked questions
Doubling the voltage halves the current for the same power. Because resistive voltage drop equals I × R, halving the current halves the absolute drop — or equivalently, you can run the wire twice as far and stay within the same percentage drop, using the same wire gauge.
Most engineers use 3 % (0.72 V) as the maximum. Some sensitive electronics require ≤ 2 % (0.48 V). The calculator lets you set any percentage.
The formula is the same for any DC voltage — just use the 12V Wire Size calculator or the 220V Wire Size calculator and enter your actual voltage and 3 % drop limit. The 24V calculator is pre-set to 24 V.
TG we-Calculate Editorial Team. (2026). 24V Wire Size Calculator — DC Gauge & Voltage Drop [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/24v-wire-size-calculator
TG we-Calculate Editorial Team. "24V Wire Size Calculator — DC Gauge & Voltage Drop." TG we-Calculate. 2026. https://we-calculate.com/calculator/24v-wire-size-calculator.
TG we-Calculate Editorial Team, "24V Wire Size Calculator — DC Gauge & Voltage Drop," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/24v-wire-size-calculator
@misc{wecalculate_24v_wire_size_calculator, title = {24V Wire Size Calculator — DC Gauge & Voltage Drop}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/24v-wire-size-calculator}}, year = {2026}, note = {TG we-Calculate} }
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