Wire Gauge AWG Calculator

This tool calculates key electrical and physical properties of copper wire based on AWG size: nominal diameter (mm/in), cross-sectional area (mm²), resistance per meter (Ω/m) at specified ambient temperature, total resistance (Ω), and maximum recommended current capacity (A) per NEC 2023 guidelines for chassis wiring. All results are derived from standardized AWG formulas and resistivity data for annealed copper.

Copper’s resistivity increases with temperature — a ~0.393% rise per °C above 20°C. The calculator adjusts resistivity (ρ) using ρ = ρ₂₀ × [1 + α(T − 20)], where α = 0.00393/°C, ensuring accurate resistance and voltage drop estimates for real-world operating conditions.

The tool accepts AWG values from 0 to 40 — covering common solid and stranded copper conductors used in electronics, power distribution, and automotive applications. Note: AWG 00 (2/0), 000 (3/0), and 0000 (4/0) are not supported; use equivalent AWG −1, −2, −3, or −4 for those sizes if needed.

Current ratings follow the NEC Table 310.16 “Allowable Ampacities of Insulated Conductors” for 75°C THHN/THWN-2 copper wire in free air (chassis wiring), derated for ambient temperature >30°C. It does not account for bundling, conduit fill, or continuous load derating — those require manual NEC compliance checks.

No — the calculator assumes annealed copper (ρ₂₀ = 1.724×10⁻⁸ Ω·m). Aluminum has ~61% higher resistivity and different thermal characteristics. For aluminum, use a dedicated Al conductor calculator or manually scale resistance by 1.63× and reduce ampacity by ~20–25% per NEC guidelines.

A voltage drop >3% (for branch circuits) suggests undersized wire. Increase AWG (i.e., lower gauge number) to reduce resistance. Use the calculator iteratively: enter a larger wire size (e.g., from AWG 18 → 16), re-calculate total resistance and voltage drop (Vₚ = I × R), and verify it meets your application’s tolerance.

AWG is logarithmic and inverse: smaller AWG numbers indicate larger diameters and greater cross-sectional area. Since resistance R ∝ 1/A, doubling the area (e.g., going from AWG 20 to AWG 17) roughly halves the resistance per unit length — making lower AWG ideal for high-current or long-run applications.

No — the calculator uses nominal AWG diameter and area, which assume solid round conductors. Stranded wire has ~1–2% higher effective resistance due to lay-length and inter-strand gaps. For precision designs, apply a 1.01–1.02 multiplication factor to calculated resistance when using finely stranded wire.

This value reflects the *continuous* current limit for un-bundled, single-conductor copper wire in free air, based on thermal limits (75°C insulation rating). It is not a safety fuse rating — always pair with appropriate overcurrent protection (e.g., breaker or fuse sized ≤125% of continuous load current per NEC 210.19(A)(1)).

Avoid entering AWG as a string (e.g., “12 AWG”) — only numeric values 0–40 are accepted. Double-check units: length must be in meters (not feet), and temperature in °C. Also remember: this tool doesn’t validate NEC installation methods — conduit fill, termination ratings, and environmental factors require separate engineering review.