2023 NEC · 324 worked scenarios

Wire size by load and distance.

Pick the load and the run length and read the answer. Every page below sizes the conductor for ampacity and for a 3% voltage drop over the distance, in copper and aluminum, and says which of the two governs. If your conditions differ, the calculator takes them all.

324

Load and distance combinations

Load currents, 15 A to 200 A

Run lengths, 25 ft to 400 ft

Long runs where drop usually governs

NEC 2023Every scenario linked below is transcribed from the 2023 NEC (NFPA 70, 2023). The code is republished on a three-year cycle and adoption varies by jurisdiction - confirm against your locally adopted edition and your authority having jurisdiction (AHJ) before you build.

120 V single phase

120 V branch circuits

240 V single phase

240 V circuits, feeders, and subpanels

15 A

25 ft 50 ft 75 ft 100 ft 125 ft 150 ft 175 ft 200 ft 250 ft 300 ft 350 ft 400 ft

20 A

25 ft 50 ft 75 ft 100 ft 125 ft 150 ft 175 ft 200 ft 250 ft 300 ft 350 ft 400 ft

25 A

25 ft 50 ft 75 ft 100 ft 125 ft 150 ft 175 ft 200 ft 250 ft 300 ft 350 ft 400 ft

30 A

25 ft 50 ft 75 ft 100 ft 125 ft 150 ft 175 ft 200 ft 250 ft 300 ft 350 ft 400 ft

35 A

25 ft 50 ft 75 ft 100 ft 125 ft 150 ft 175 ft 200 ft 250 ft 300 ft 350 ft 400 ft

40 A

25 ft 50 ft 75 ft 100 ft 125 ft 150 ft 175 ft 200 ft 250 ft 300 ft 350 ft 400 ft

45 A

25 ft 50 ft 75 ft 100 ft 125 ft 150 ft 175 ft 200 ft 250 ft 300 ft 350 ft 400 ft

50 A

25 ft 50 ft 75 ft 100 ft 125 ft 150 ft 175 ft 200 ft 250 ft 300 ft 350 ft 400 ft

60 A

25 ft 50 ft 75 ft 100 ft 125 ft 150 ft 175 ft 200 ft 250 ft 300 ft 350 ft 400 ft

70 A

25 ft 50 ft 75 ft 100 ft 125 ft 150 ft 175 ft 200 ft 250 ft 300 ft 350 ft 400 ft

80 A

25 ft 50 ft 75 ft 100 ft 125 ft 150 ft 175 ft 200 ft 250 ft 300 ft 350 ft 400 ft

90 A

25 ft 50 ft 75 ft 100 ft 125 ft 150 ft 175 ft 200 ft 250 ft 300 ft 350 ft 400 ft

100 A

25 ft 50 ft 75 ft 100 ft 125 ft 150 ft 175 ft 200 ft 250 ft 300 ft 350 ft 400 ft

110 A

25 ft 50 ft 75 ft 100 ft 125 ft 150 ft 175 ft 200 ft 250 ft 300 ft 350 ft 400 ft

125 A

25 ft 50 ft 75 ft 100 ft 125 ft 150 ft 175 ft 200 ft 250 ft 300 ft 350 ft 400 ft

150 A

25 ft 50 ft 75 ft 100 ft 125 ft 150 ft 175 ft 200 ft 250 ft 300 ft 350 ft 400 ft

175 A

25 ft 50 ft 75 ft 100 ft 125 ft 150 ft 175 ft 200 ft 250 ft 300 ft 350 ft 400 ft

200 A

25 ft 50 ft 75 ft 100 ft 125 ft 150 ft 175 ft 200 ft 250 ft 300 ft 350 ft 400 ft

Long runs

Where voltage drop takes over

Past roughly 300 feet, ampacity usually stops being the binding requirement. The conductor that safely carries the current will still deliver too little voltage at the far end, so the size goes up on performance grounds - a detached shop, a well pump, a barn, an EV charger at the end of a long driveway. Voltage-drop limits are recommendations in the 2023 NEC rather than requirements, though specifications and some jurisdictions enforce them. For what the figure means and why 120 V runs suffer twice as badly, read what voltage drop is and when it matters.

Every figure on this page comes from the 2023 NEC (NFPA 70, 2023). The code is republished on a three-year cycle and adoption varies by jurisdiction - confirm against your locally adopted edition and your authority having jurisdiction (AHJ) before you build.

Reference estimate - verify before you build. AmpSizer reports reference estimates transcribed from published tables in the 2023 NEC (NFPA 70, 2023), and from no other edition. It is not a substitute for the code adopted in your jurisdiction. The code is republished on a three-year cycle and adoption varies by jurisdiction - confirm against your locally adopted edition and your authority having jurisdiction (AHJ) before you build. Final conductor sizing, overcurrent protection, and installation must be determined by a licensed electrician and approved by your AHJ.

Jurisdictions adopt editions on their own schedule and frequently amend them, so the edition enforced where you work may not be the one cited here. Confirm which edition and which local amendments apply to your job before relying on any value on this page.