Wire Size by Run Distance
The distance between the electrical panel and the load is one of the most critical factors in wire sizing. Voltage drop increases linearly with distance, meaning a conductor that works perfectly at 50 feet may be inadequate at 150 feet. This section provides pre-computed wire sizing tables organized by run distance, covering every common distance from 25 feet to 500 feet. Each page shows the recommended wire gauge for all standard voltages and amperages at that specific distance, making it easy to find the correct conductor without performing manual calculations.
Select Your Run Distance
Choose the one-way distance from your electrical panel to the load. This is the straight-line conductor length, not the distance as measured on a floor plan. Account for vertical runs through walls, horizontal runs in attics or crawlspaces, and any additional conductor length needed for making connections at both ends. As a rule of thumb, add 10-20% to the measured distance to account for routing, turns, and service loops.
25 Feet
A 25-foot conductor run is a short distance found in most indoor residential circuits. At this length, voltage drop is rarely a concern for standard branch circ...
View Wire Sizes →50 Feet
A 50-foot conductor run is typical for most residential branch circuits within the main structure. This distance covers the average run from an electrical panel...
View Wire Sizes →75 Feet
A 75-foot conductor run is common for circuits reaching the far side of a larger home or running to an attached garage. At this distance, voltage drop calculati...
View Wire Sizes →100 Feet
A 100-foot conductor run is a common distance for circuits to detached garages, workshops, and outbuildings close to the main structure. Voltage drop becomes a ...
View Wire Sizes →125 Feet
A 125-foot conductor run is typical for circuits to medium-distance outbuildings, detached garages set back from the house, well pumps near the property, and RV...
View Wire Sizes →150 Feet
A 150-foot conductor run is common for well pump circuits, larger detached workshops, and subpanel feeders to buildings set further from the main service. Volta...
View Wire Sizes →200 Feet
A 200-foot conductor run is typical for circuits to distant outbuildings, barns, well houses, and pool equipment rooms located away from the main structure. At ...
View Wire Sizes →250 Feet
A 250-foot conductor run is a long distance found in rural properties feeding detached structures, barn circuits, well pumps at the back of a large lot, and agr...
View Wire Sizes →300 Feet
A 300-foot conductor run is common in agricultural settings, large rural properties, and commercial sites with outbuildings far from the main electrical service...
View Wire Sizes →400 Feet
A 400-foot conductor run is a very long distance encountered in farms, ranches, commercial campgrounds, and large industrial sites. At this length, the conducto...
View Wire Sizes →500 Feet
A 500-foot conductor run is among the longest distances encountered in residential and light commercial installations. At this extreme distance, voltage drop is...
View Wire Sizes →How Distance Affects Wire Sizing
Voltage drop is directly proportional to conductor length. If you double the distance, you double the voltage drop. This linear relationship means that a circuit that has 2% voltage drop at 50 feet will have 4% voltage drop at 100 feet and 8% at 200 feet with the same wire gauge. To maintain acceptable voltage drop at longer distances, you must increase the conductor size, which reduces resistance per foot and brings the total voltage drop back within limits.
The standard voltage drop formula for single-phase circuits is Vd = (2 x R x D x I) / 1000, where R is resistance in ohms per 1000 feet, D is the one-way distance in feet, and I is current in amperes. The factor of 2 accounts for both the outgoing and return conductors. For three-phase circuits, the factor changes to 1.732. The distance D in this formula is always the one-way distance from the source to the load, not the total wire length.
For short runs under 50 feet, the NEC minimum wire gauge based on ampacity is usually adequate, and voltage drop is rarely a concern. Between 50 and 100 feet, voltage drop starts to become relevant for 120-volt circuits, and you may need to upsize by one gauge. Between 100 and 200 feet, voltage drop typically controls the wire size for most amperages, often requiring two or more sizes larger than the ampacity minimum. Beyond 200 feet, the conductor size and cost increase rapidly, and alternative strategies like higher voltage distribution or closer panel placement should be considered.
One often-overlooked consideration for long runs is the cost of copper versus the cost of aluminum conductors. For a 200-foot run with 4/0 AWG copper, switching to aluminum would require 250 kcmil but could save 40-60% on material costs. For feeder circuits to detached structures, aluminum is a sensible and code-compliant choice that can significantly reduce project costs. The trade-off is that aluminum requires larger conduit, special termination hardware (AL-CU rated), and anti-oxidant compound at all connections.