Conductor sizing

Wire Gauge Calculator

Selects smallest AWG meeting ampacity and voltage drop requirements.

Wire Gauge Calculator

Find the recommended wire gauge for your circuit.

Live Result
Formula-backed — instant professional result
System Type
RECOMMENDED GAUGE
0 AWG
Also equals 0 V
Formula used Selects smallest AWG meeting ampacity and voltage drop requirements. The primary result is shown in AWG using the formula displayed above. Finds the correct wire size for safety and efficiency.

This calculator is an educational planning estimate. Verify safety-critical work with equipment nameplate data, local electrical code, and a qualified professional.

Find the correct wire gauge (AWG) for your current and circuit length. Includes NEC ampacity table and voltage drop planning.

Wire and voltage drop planning

Conductor run visual

Find the correct wire gauge (AWG) for your current and circuit length. Includes NEC ampacity table and voltage drop planning.

AC/DC single-phase formula-first page-specific visual

Wire Gauge Calculator — AWG & Ampacity Chart | Ampstowatt Guide

Conductor planning map

Current, distance, conductor material, and voltage drop

Wire and voltage-drop pages rank better when the content shows the physical run: source, conductor length, voltage loss, and load.

Formula Select smallest ampacity that keeps voltage drop below target
Wire Gauge Calculator — AWG & Ampacity Chart | Ampstowatt technical circuit diagram A premium electrical diagram showing the main values and conversion flow for Wire Gauge Calculator — AWG & Ampacity Chart | Ampstowatt. Source Current One-way distance Copper / aluminum Load % voltage drop
Wire Gauge Calculator — AWG & Ampacity Chart | Ampstowatt Conductor planning map with real formula values and planning checkpoints.

Quick answer

Use this calculator to choose a practical wire gauge for current and distance.

Wire gauge selection should consider both ampacity and voltage drop. The calculator helps narrow the planning range before final code and installation checks.

Select smallest ampacity that keeps voltage drop below target

Inputs to check before calculating

  • Enter continuous current, not only short startup current.
  • Set the voltage and allowed drop for the equipment being powered.
  • Choose conductor material and installation conditions carefully.
  • Verify terminal ratings, insulation, bundling, and ambient temperature.

Example: choosing a practical wire gauge

Start with current, distance, voltage, conductor material, and allowed voltage drop. The calculator gives a planning reference, but final conductor sizing must account for ampacity, temperature, bundling, terminals, and local code.

Best use cases

  • Ampacity reference
  • Voltage-drop check
  • Copper and aluminum options
  • single-phase AC load planning with clear unit labels.

Common mistake to avoid

Do not choose wire from ampacity alone on long runs; voltage drop may require a larger conductor.

How to use the result

Use the recommendation as a planning reference, then verify the final conductor against local electrical code.

Accuracy and safety note

Calculator output is a planning estimate. Final breaker sizing, wire gauge, derating, voltage-drop limits, equipment protection, and code compliance should be verified with manufacturer documentation and a qualified electrician or engineer.

For the broad formula, reference table, and breaker planning context, start with the main Amps to Watts Calculator.

Technical Diagram

Wire Gauge Calculator Formula Map

Size by amps + distance + voltage drop

Check ampacity first, then voltage drop. Use the calculator on this page to change the inputs and verify the result before sizing equipment.

Wire, Safety & Power Quality Tools

Start with the main conversion tool

After calculating watts and amps, use these pages to check conductor sizing, voltage loss, power factor, and high-current equipment planning.Amps to Watts Calculator

Methodology, Review Notes, and Sources

How this calculator works

The calculator applies Watt's law for DC and resistive loads, then adds power factor for AC loads and the 1.732 multiplier for balanced three-phase line-to-line calculations.

  • DC and resistive loads: W = A x V
  • Single-phase AC: W = A x V x PF
  • Three-phase AC: W = 1.732 x A x V x PF

Editorial review

Last reviewed: June 26, 2026. Ampstowatt.com is built around the amps to watts conversion — our core specialty. Content is maintained by the Ampstowatt editorial team and checked for formula consistency, unit labels, calculator behavior, and safety wording.

The page is an educational planning reference, not a licensed electrical design or inspection service.

Reference sources

FAQ

Wire Gauge FAQ

Fast answers before you use the calculator or compare formulas.

AWG How do I choose the right wire gauge?

Wire gauge selection must satisfy two independent requirements: ampacity (the wire must carry the load current without overheating) and voltage drop (the wire must deliver adequate voltage at the load). Check both, and use the larger wire if the two requirements disagree. The calculator checks both simultaneously.

SIZE What is the difference between wire gauge and wire size?

In the American Wire Gauge (AWG) system, gauge and size are inversely related — a lower gauge number means a larger wire. 14 AWG is smaller than 10 AWG. Outside North America, wire is sized by cross-sectional area in mm². 14 AWG ≈ 2.08 mm², 10 AWG ≈ 5.26 mm².

20A What gauge wire for 20 amps?

Per NEC Table 310.16, 12 AWG copper wire (rated 20A at 60°C) is the minimum for a 20A circuit. For runs longer than 50 feet at 120V, voltage drop may require 10 AWG. At 240V, 12 AWG is usually sufficient for longer runs. Always verify with local code and installation conditions.

30A What gauge wire for 30 amps?

10 AWG copper is rated for 30A at 60°C per NEC Table 310.16. For dryer circuits, the NEC specifies a minimum of 10 AWG. For long runs to outbuildings or sub-panels, 8 AWG may be needed to limit voltage drop. Aluminum requires 8 AWG minimum for 30A.

TEMP Does ambient temperature affect wire gauge selection?

Yes. NEC Table 310.15(B)(1) provides derating factors for ambient temperatures above 30°C (86°F). At 40°C, 60°C-rated wire must be derated to 82% of its table ampacity. At 50°C, it drops to 58%. In hot attics, conduit in sun, or industrial environments, you may need to upsize the wire by one or two gauges.

FILL How does conduit fill affect wire ampacity?

Running multiple current-carrying conductors in the same conduit generates heat. NEC 310.15(C)(1) requires derating when more than 3 conductors share a conduit: 4–6 conductors = 80%, 7–9 = 70%, 10–20 = 50%. This can require larger wire than a single-circuit installation.