Wire and Cable Calculator

Electrical Engineering & NEC 2023 Wire Sizing Metrology

Conductor sizing balances thermodynamic ampacity heating and Ohm's Law voltage drop:

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• NEC Voltage Drop Formula (Single-Phase Circuits)**:

$$\Delta V = \frac{2 \times K \times I \times L}{\text{CMIL}}$$

$$\% \text{Voltage Drop} = \left(\frac{\Delta V}{V_{\text{nominal}}}\right) \times 100$$

• Resistivity Constants ($K$): Copper $K = 12.9\ \Omega\cdot\text{cmil/ft}$ | Aluminum $K = 21.2\ \Omega\cdot\text{cmil/ft}$

• NEC Section 210.19 Limit: Maximum $3\%$ drop on branch circuits.

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• NEC Table 310.16 Standard Conductor Capacities & Circular Mils**:

• 14 AWG ($4,110\text{ CMIL}$): $15\text{ Amps}$ (Copper)

• 12 AWG ($6,530\text{ CMIL}$): $20\text{ Amps}$ (Copper) / $15\text{ Amps}$ (Aluminum)

• 10 AWG ($10,380\text{ CMIL}$): $30\text{ Amps}$ (Copper) / $25\text{ Amps}$ (Aluminum)

• 8 AWG ($16,510\text{ CMIL}$): $50\text{ Amps}$ (Copper) / $40\text{ Amps}$ (Aluminum)

• 6 AWG ($26,240\text{ CMIL}$): $65\text{ Amps}$ (Copper) / $50\text{ Amps}$ (Aluminum)

• 4 AWG ($41,740\text{ CMIL}$): $85\text{ Amps}$ (Copper) / $65\text{ Amps}$ (Aluminum)

• 2 AWG ($66,360\text{ CMIL}$): $115\text{ Amps}$ (Copper) / $90\text{ Amps}$ (Aluminum)

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• Standard Circuit Sizing Benchmarks**:

• 15A Shed Run (120V, 100 ft, Cu): 10 AWG | 1.99% Drop | 15A Breaker

• 20A Circuit (120V, 75 ft, Cu): 8 AWG | 1.95% Drop | 20A Breaker

• 50A EV Charger (240V, 60 ft, Cu): 6 AWG | 1.31% Drop | 50A Breaker

• 60A Subpanel (240V, 150 ft, Al): 2 AWG Al | 2.29% Drop | 60A Breaker

How to Use This Calculator

Enter Circuit Voltage & Phase, Circuit Load Current (Amperes), One-Way Distance from Panel, Conductor Material into the input fields and the calculator will instantly compute Recommended Wire Gauge, Estimated Voltage Drop (%). All calculations happen in real time — no submission or page reload required. You can adjust any input value and see the result update immediately.

Understanding Your Result

The Wire and Cable result gives you a precise, calculated value based on the inputs you provide. Compare your result against published benchmarks from IRC, NAHB, and local building codes to assess where you stand. A single calculation is a useful starting point, but tracking this metric over time — as inputs change — gives you a much more complete picture.

Practical Application

The Wire and Cable is most useful when you have specific, real-world data to enter. For example: enter your actual Circuit Voltage & Phase to calculate your recommended wire gauge. The result helps homeowners, contractors, project managers, and architects make informed decisions about estimating material quantities, project costs, and construction planning. This calculator is trusted by professionals and individuals alike because it follows the exact formulas validated by IRC, NAHB, and local building codes.

Accuracy Notes and Limitations

Add a 10–15% waste buffer to all material estimates. Always verify with local building codes and a licensed contractor. The accuracy of any calculator is limited by the quality of the inputs provided. Double-check your units before entering values — unit errors are the most common source of incorrect results. For critical decisions, cross-reference with at least one additional source or professional consultation.

Frequently Used With

This calculator is often used alongside other construction tools to build a complete analytical picture. Combining multiple related calculations provides stronger evidence for decisions than relying on any single metric. Browse the Construction category to find complementary calculators for your specific use case.