Wire Gauge Calculator
Find the right wire gauge for amperage and distance
Breaker rating
120V or 240V
Distance from panel to load
NEC recommends max 3%
Recommended Wire Gauge
—
AWG
Actual Voltage Drop
—
%
Voltage at Load
—
V
Wire Type
—
Disclaimer: Results are estimates based on standard formulas. Not a substitute for professional advice from a licensed contractor, engineer, or architect. Verify all calculations before making purchasing or construction decisions.
How to Use This Calculator
Our wire gauge calculator follows NEC guidelines to recommend correct wire size.
- Identify circuit amperage
- Determine voltage
- Measure wire length
- Enter specifications
- Follow local codes
Expert Insights
Smart analysis for your Electrical project
80% Load Rule Enforcement
NEC requires circuits loaded to no more than 80% of breaker rating for continuous loads. AI enforces this automatically in all calculations.
GFCI/AFCI Requirements
GFCI: kitchens, baths, garages, outdoors. AFCI: bedrooms, living areas (2023 NEC). AI flags required protection for your circuit type.
Voltage Drop Optimization
Over 3% drop causes motor overheating. AI recommends wire gauge upgrades when your run length would cause excessive voltage drop.
Calculation Formula
Voltage drop = (2 x Length x Current x Resistance) / 1000
Minimum gauge based on NEC Table 310.16
Authority References
Our calculations are based on guidelines and standards from these authoritative sources:
- National Fire Protection Association (NFPA) — NFPA 70 — National Electrical Code (NEC). Learn more
- Underwriters Laboratories (UL) — Wire & Cable Safety Standards. Learn more
Frequently Asked Questions
What wire gauge for 20 amp circuit?
12 AWG copper for 20 amp circuits up to 100 ft. Step up to 10 AWG for longer runs.
What happens if wire gauge is too small?
Undersized wire causes overheating, voltage drop, and fire hazard.