Wire Size Calculator for DC Circuits – mm², AWG & Voltage Drop
This free DC wire size calculator instantly determines the minimum cable thickness in mm² based on length, voltage drop, power, and current. Get accurate results with AWG and SWG equivalents for copper or aluminum conductors — perfect for solar, RV, camper, marine, and off-grid projects.
How to Use This DC Wire Size Calculator
- Enter wire length (meters, cm, feet, or inches)
- Select voltage drop (2% is standard for DC)
- Fill in 2 of: Power (W), Voltage (V), Current (A)
- Get instant mm² + AWG + SWG recommendation
Common DC Applications
- Solar panel to charge controller
- Caravan, camper or RV battery wiring
- Marine DC systems
- Off-grid power setups
- Home battery system setups
FAQ – DC Wire Size Calculator
A DC wire size calculator determines the minimum cable thickness (mm²) needed for safe and efficient
power delivery in direct current systems. It factors in cable length, voltage drop, power, and current
to recommend the correct wire gauge.
No. This tool is intended only for DC circuits. AC wiring follows different standards and is regulated
by national electrical codes. For household or industrial AC systems, always follow local code or
consult a licensed electrician.
Enter your cable length, desired maximum voltage drop (e.g., 2%), and two of the following: power (W),
voltage (V), or current (A). The calculator automatically determines the required cross-sectional
area (mm²) and provides AWG/SWG equivalents.
A voltage drop of 2–3% is standard for most DC applications such as solar systems, RVs, and marine
installations. Critical systems may use 1%, while short or low-power circuits can sometimes allow 5–10%.
Longer cables increase resistance and therefore voltage drop. As cable length grows, you often need a
thicker cable (higher mm²) to maintain efficiency and prevent overheating. Doubling the cable length can
require doubling the wire cross-section.
Excessive voltage drop reduces system efficiency and can cause devices to underperform, shut down, or
overheat. Low-voltage DC systems (such as 12V or 24V) are especially sensitive to voltage drop, so correct
wire sizing is critical for safety and performance.