EV Charger Wire Size Calculator
// SIZE EVSE BRANCH-CIRCUIT WIRE, BREAKER, AND VOLTAGE DROP FROM CHARGER CURRENT, RUN LENGTH, MATERIAL, AND DERATING INPUTS //
Charger output in amps.
Panel to charger, in feet.
Degrees C.
Percent voltage drop.
Based on 125% of EVSE output current.
copper, 13.3 mm2
6 AWG passes the continuous-load ampacity screen, the selected breaker check, and the 3.00% voltage-drop target.
EVSE output is treated as a continuous load, so the calculator uses 125% of charger current for the ampacity and breaker screen.
Conductor ampacity uses common NEC Table 310.16 values with simplified ambient and current-carrying conductor adjustments.
Small-conductor overcurrent limits are screened for 14, 12, and 10 AWG where applicable.
The voltage-drop estimate uses charger current, conductor resistance, and round-trip circuit length.
Voltage drop is a performance target, not the same thing as minimum safety ampacity. Long garage, driveway, and parking-area runs may need upsizing.
Ampacity-only first passing size: 6 AWG.
Verify the charger installation manual, terminal ratings, insulation type, conduit fill, grounding, GFCI protection, and local amendments.
Confirm panel capacity and load calculations before adding EV charging. A larger conductor does not solve an overloaded service or feeder.
Estimated drop on selected size: 3.54 V.
Check long EV charger runs when voltage drop, not ampacity, controls the wire size.
Review conductor ampacity with insulation, ambient temperature, and raceway derating.
Verify raceway fill for EV charger conductors and equipment grounding conductors.
Run a general cable-sizing check for feeders, subpanels, and branch circuits.
Estimate resistance and heat loss for a selected conductor size.
Estimate copper or aluminum weight for long garage, driveway, and parking runs.