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Solar Panel PV Wire Sizing Calculator

Calculate the minimum conductor cross-sectional area needed for a PV circuit run at a target maximum voltage drop.

Computed in your browser — nothing you enter is uploaded. Figures are presented in United States units and terminology, and each formula’s basis is cited under regulatory standards below.

Last verified 2026-08-26 · v1.0.0

Market
Imperial · sales tax

Minimum conductor cross-sectional area

5.45 mm²

Check your inputs

Convert the resulting minimum cross-sectional area to the next larger standard wire gauge (AWG) or metric conductor size — do not round down. Also verify the selected conductor's ampacity rating (NEC Table 310.16, with appropriate temperature/conduit fill derating) independently meets or exceeds the circuit current.

At the values currently entered, the minimum conductor cross-sectional area works out to 5.45 mm². Confidence is moderate: the method is sound, but real materials and site conditions vary. Figures are shown in United States units and terminology; switch the market above if you are building elsewhere.

Add the equipment this sizes

This result is a specification — 5.45 mm² — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.

Preliminary estimate, not certified engineering. This tool produces an indicative quantity calculation for planning purposes only — it is not a certified structural analysis, a guaranteed material takeoff, or a substitute for building department approval. Always verify measurements on-site and have a licensed contractor or structural engineer review any load-bearing, code-sensitive, or safety-critical work before purchasing materials or starting construction. Spotted an arithmetic or standards error? Report it to contact@craftquantities.com with your inputs — a confirmed fix gets a permanent check of its own, so the same mistake cannot come back.

Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.

Regulatory standards & verification citations

  • Conductor area = (2 x resistivity x one-way distance x current) ÷ maximum allowable voltage drop, the standard DC circuit voltage-drop sizing method applied to a solar PV source/output circuit run (the factor of 2 accounts for the round-trip conductor length)

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Frequently asked questions

Why does the formula multiply the distance by 2?
The factor of 2 accounts for the round-trip conductor length — current flows out to the load through one conductor and back through the other, so both directions' resistance contribute to the voltage drop.
Should I round the result down to the nearest standard wire size?
No — always round up to the next larger standard wire gauge (AWG) or metric conductor size. Rounding down would result in a smaller conductor than the minimum needed to stay within your target voltage drop.
Does meeting the voltage drop target mean the wire is properly sized?
Not by itself — you also need to independently verify the selected conductor's ampacity rating (per NEC Table 310.16, with appropriate temperature and conduit fill derating) meets or exceeds the circuit current, since voltage-drop sizing and ampacity sizing are separate checks.