Wire Size Calculator – DC Voltage Drop, AWG & mm² Cable Size

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.

Calculate the minimum wire size for DC circuits. Enter length, voltage drop, and at least two of power, voltage, or current.

How to Use This DC Wire Size Calculator

  1. Enter wire length (meters, cm, feet, or inches)
  2. Select voltage drop (2% is standard for DC)
  3. Fill in 2 of: Power (W), Voltage (V), Current (A)
  4. 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

Frequently Asked Questions (FAQ)

What is a 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, based on length, voltage drop, power, and current.

Can I use this calculator for AC (alternating current) circuits?

No. This tool is intended for DC circuits. For household or industrial AC wiring, always follow national electrical codes and/or consult a licensed electrician.

How do I calculate wire size for DC voltage drop?

Enter your cable length, desired voltage drop (e.g., 2%), and two of: power (W), voltage (V), or current (A). The tool instantly shows the required mm² and AWG/SWG equivalents.

What is the best voltage drop for DC circuits?

2–3% is standard for most DC applications like solar panels, RVs, and marine systems. Lower values (1%) are used for critical systems; higher (5–10%) for short, low-power runs.

How does cable length affect DC wire size?

Longer cables increase resistance and voltage drop. Double the length → may need double the cross-section to maintain efficiency.

Why Voltage Drop Matters in DC

Excessive voltage drop can lead to power loss, overheating, reduced device performance, and safety hazards. Correct wire sizing ensures efficient energy delivery and long-term system reliability, especially in low-voltage or long-distance setups.

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