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There is no single maximum distance for 10 AWG wire on a 30-amp circuit. The usable run depends on circuit voltage, actual load, conductor material and installation, and the voltage-drop limit used. As examples—not universal limits—one chart lists 48 feet one way at 120 volts and 96 feet at 240 volts for 10 AWG copper carrying 30 amps at a 3% voltage-drop target. A Southwire guide lists 45 feet for 10 AWG copper at 30 amps in a 110-volt table. Those figures use different stated voltages and may use different calculation assumptions, so they should not be treated as interchangeable cutoffs.
Why the maximum distance depends on more than wire gauge
Wire gauge describes conductor size, but it does not by itself establish how far a circuit can run. Voltage drop increases with route length and current, and its percentage depends on the circuit voltage. Conductor material and resistance assumptions also affect the calculation. A number from a distance chart is meaningful only alongside the conditions used to produce it.
For the same conductor and current, a higher circuit voltage can allow a longer run for the same percentage voltage-drop target. In ElectricalToolbox’s chart, the listed 240-volt distance is twice the 120-volt distance. That relationship illustrates the voltage effect; it does not make either figure a general allowance for other loads or installations.
Published distance examples for 10 AWG copper at 30 amps
| Source and stated conditions | Listed distance | How to interpret it |
|---|---|---|
| ElectricalToolbox chart: 120 V, single phase, 30 A, 3% target; unity power factor and 75°C basis | 48 ft one way | A chart example using those stated calculation assumptions. ElectricalToolbox voltage-drop chart |
| ElectricalToolbox chart: 240 V, single phase, 30 A, 3% target; unity power factor and 75°C basis | 96 ft one way | Shows how the listed distance changes with voltage in this chart. ElectricalToolbox voltage-drop chart |
| Southwire guide: 110 V, single phase, 30 A, recommended 3% drop | 45 ft | A separate manufacturer chart example; its result should not be silently combined with the ElectricalToolbox figures. Southwire guide hosted by The Home Depot |
The 48-foot and 45-foot results are not a direct contradiction: they state different voltages, and the tables do not establish identical calculation assumptions. When comparing any two estimates, line up the actual circuit voltage, current, conductor material, one-way route length, resistance or temperature basis, and allowed voltage-drop percentage.
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Voltage drop and ampacity are separate checks
A wire can satisfy an ampacity or overcurrent-protection check and still have more voltage drop than desired over a long run. Conversely, a voltage-drop example alone does not establish that a conductor is correctly sized or protected for an installation. A circuit design needs to account for both constraints, using the more limiting result.
ElectricalToolbox’s separate discussion of a 200-foot, 30-amp circuit addresses the distinction between selecting a wire for ampacity and accounting for voltage drop; it is not a universal prescription for every 30-amp run. ElectricalToolbox: Wire Size for a 200 ft, 30 Amp Circuit
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What voltage-drop targets mean
The NFPA-hosted supporting material for Standards Council Agenda Item 25-8-6(k)(1), published in 2025, says: “The NEC recommends that the maximum combined voltage drop for both the feeder and branch circuit should not exceed 5%, and the maximum on the branch circuit shouldn’t exceed 3%.” The document reports these as recommendations. They should not be presented as a mandatory universal maximum for every circuit; applicable requirements depend on the adopted code and installation. NFPA supporting material (2025)
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Installation details that can change wire selection
Distance is only one part of conductor sizing. The Copper Development Association’s installation guidance describes factors including continuous-load calculations, ambient-temperature correction, the number of current-carrying conductors, terminal temperature ratings, and overcurrent protection. A change in any of these conditions can affect the selection; a chart for a simple example cannot settle the requirements for a specific job.
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Before choosing wire or treating a chart distance as a limit, establish:
- Actual system voltage and expected load current.
- One-way route length and conductor material.
- Cable or conductor type, installation conditions, and applicable temperature or resistance basis.
- The desired voltage-drop target and whether the run is part of a feeder, branch circuit, or both.
- Continuous-load sizing, conductor count, terminal ratings, overcurrent protection, and locally adopted code requirements.
The Copper Development Association guide explains these installation considerations and illustrates how they can change conductor selection. Its example is not a blanket instruction for a different circuit. Copper Development Association: Recommended Practices for Installing Copper Building Wire
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How to use a distance chart for your run
- Confirm the circuit conditions. Determine voltage, expected current, conductor material, cable type, and actual one-way route length rather than relying on a generic “30 amp” description.
- Choose the voltage-drop target. A chart’s result changes with its stated target; do not assume the percentage or whether it covers a branch circuit or a larger feeder-and-branch combination.
- Check the chart’s assumptions. Compare temperature or resistance basis and other calculation inputs. If the chart does not state enough to match your installation, treat its distance as an example, not a design answer.
- Verify ampacity and installation compliance separately. Account for load characteristics, continuous operation where applicable, conductor count, ambient conditions, terminations, overcurrent protection, and the locally adopted code.
- Have the complete circuit evaluated when details are uncertain. A qualified electrician or electrical designer can calculate voltage drop and confirm conductor and protection choices for the actual route and jurisdiction.
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