Size the wire.
See what matters.
Current capacity, voltage drop and AC losses.
One calculation, every constraint in view.
Gauge comparison
Click a row to inspect| Size | mm² | Allowable A | Drop % | Loss W | Metal kg* | Check |
|---|
*Conductor metal only for the selected weight count and one-way length; excludes insulation and shields.
Calculation method & reference data
This is a preliminary engineering sizing tool, not a compliance check. Reference ampacities, temperature factors and bundle factors are from published LAPP Tannehill tables and Cerrowire aluminum tables, both identified by their publishers as based on the 2017 NEC. Confirm the applicable edition and installation rules.
Table mode uses 75°C or 90°C columns. Ampacity = minimum of temperature- and bundle-adjusted ampacity divided by √(Rac/Rdc), termination-column ampacity, and small-conductor caps. The tool conservatively caps copper 14/12/10 AWG at 15/20/30 A and aluminum 12/10 at 15/25 A. These caps are not breaker selections. The chosen sizing allowance is applied to the full load before comparison.
Manufacturer mode checks only the selected gauge. It estimates temperature correction with √[(Tmax − Tamb)/(Tmax − Tref)]. This constant thermal-resistance approximation requires validation against the manufacturer's curve; no ampacity is inferred for other gauges.
Manufacturer R + jX overrides estimated resistance and inductance for voltage drop and losses. Ω/km and mΩ/m are divided by 1000; Ω/1000 ft is divided by 304.8. Frequency must match the circuit. Temperature is recorded and must lie between ambient and the wire limit; no resistance extrapolation is made. Supplied ampacity must already cover AC heating at that frequency, so only ambient and bundle derating apply. Impedance alone cannot establish ampacity.
Metal mass = cross-sectional area × one-way length × conductor count × density. Copper density is 8,960 kg/m³; aluminum is 2,700 kg/m³. AWG areas are ideal nominal areas. Manufacturer mass is the specified mass per length × one-way length × conductor count (single-core) or complete cable runs (multicore). Weight settings do not change ampacity, losses or electrical conductor counts.
Rdc = ρ20[1 + α(T − 20)]L/A. Resistance is calculated at the selected wire temperature limit, not a predicted equilibrium temperature. Round-conductor internal impedance supplies the skin-effect factor; ordinary stranded wire is approximated by an equivalent solid round conductor. Litz, magnetic armor, proximity losses, harmonics and transient heating need a more detailed model. Copper: ρ20 = 1.7241×10⁻⁸ Ωm, α = 0.00393/°C; aluminum: 2.8264×10⁻⁸ Ωm, 0.00403/°C.
Approximate AC drop = k I L(R′ cosφ + X′ sinφ), where k = √3 for balanced three-phase and 2 for single-phase. DC drop = 2 I L R′. X′ = 2πfL′. Copper loss = 3I²R′L for three-phase or 2I²R′L otherwise. Inputs use one-way length and line current. Large drop percentages need a full phasor/load calculation.
Wire insulation voltage, connector ratings, fault withstand, short-circuit protection, conduit fill, and installation-specific rules are separate checks. This model does not certify aerospace, automotive, marine or building wiring.