10 AWG ampacity by temperature column
| Conductor | 60°C | 75°C | 90°C | 240.4(D) |
|---|---|---|---|---|
| Copper | 30 A30 A breaker | 35 A30 A breaker | 40 A30 A breaker | 30 A |
| Aluminum | 25 A25 A breaker | 30 A25 A breaker | 35 A25 A breaker | 25 A |
Ampacities are NEC Table 310.16 values for a conductor at 30°C ambient in a raceway, cable, or direct burial with three or fewer current-carrying conductors. Ambient correction and conductor adjustment are applied to these numbers before the 240.4(D) cap is checked, never after it.
What size breaker for 10 gauge wire
- 10 AWG copper: 30 A, held there by 240.4(D)(7).
- 10 AWG aluminum: 25 A, held there by 240.4(D)(6).
240.4(D)(7) caps overcurrent protection on 10 AWG copper at 30 A, so the device is 30 A whatever the terminations are marked and whatever the 30 A in the 90°C column becomes after correction. The higher columns are derating arithmetic: they describe how much current the insulation survives at 30°C ambient with three current-carrying conductors, not how large a breaker the conductor will protect. Aluminum at this size is held at 25 A by 240.4(D)(6), whatever the 30 A in its 75°C column would otherwise take. 334.80 and 340.80 hold NM-B and UF-B cable to the 60°C column whatever the terminals are marked, so a cable assembly is read from the left-hand column while conductors in raceway are read from the column the equipment is listed for.
What 10 gauge wire is used for
- 30 A dryers, water heaters, and RV pedestals
- 120/240 V appliance circuits that need a neutral
- Equipment grounding conductor on 30 A through 50 A circuits
Ten gauge carries 30 A at 60°C and is capped there by 240.4(D)(7), which makes it the standard dryer, water heater, and RV-pedestal conductor. 10/3 NM-B with ground is the four-wire cable a dryer or a range receptacle needs, and the same size feeds a 30 A pedestal or a small storage water heater that 422.13 treats as a continuous load.
It is also the size that grounds most 240 V residential circuits. Table 250.122 has no 30 A, 40 A, or 50 A row, so all three land on the 60 A row, which asks for 10 AWG copper or 8 AWG aluminum. That is why 6/3 NM-B sold for a 50 A range arrives with a 10 AWG ground rather than one the size of the phase conductors.
Aluminum at this size is capped at 25 A by 240.4(D)(6), so 10 AWG aluminum is not a 30 A conductor in any column even though 310.16 lists 30 A in the 75°C column. Box fill is 2.50 cubic inches per counted conductor, and the conductors are stiff enough that a deeper box is worth the extra space. Loads above 30 A step to 8 AWG copper.
Grounding with 10 AWG
As an equipment grounding conductor, 10 AWG is sized from the overcurrent device rather than from the phase conductors. Table 250.122 names 10 AWG copper on the 60 A row and 10 AWG aluminum on the 20 A row. 250.122(B) raises the ground in the same proportion as the phase conductors when they are increased for voltage drop, and 250.122(A) caps it at the size of the conductors it runs with.
Table 250.66 never lists 10 AWG as a grounding electrode conductor, so it is used for phase conductors, neutrals, and equipment grounds rather than for the connection to earth.
Voltage drop and run limits
Chapter 9 Table 8 lists 10 AWG copper at 1.24 ohms per 1000 ft at 75°C and aluminum at 2.04 ohms per 1000 ft. Resistance is what a voltage-drop calculation multiplies by current and length, so a conductor twice as long drops twice the volts.
| Conductor | 120 V single phase | 240 V single phase | 240 V three phase |
|---|---|---|---|
| 10 AWG copper at 30 A | 45 ft | 95 ft | 110 ft |
| 10 AWG aluminum at 25 A | 35 ft | 70 ft | 80 ft |
NEC 210.19(A)(1) Informational Note 4 recommends keeping branch-circuit drop at or below 3%. The lengths above are floored to the nearest 5 ft so a listed length never exceeds the computed limit, and they leave reactance out, which makes a large conductor in steel raceway fall short. Halving the current doubles the distance.
Box fill with 10 AWG
Table 314.16(B) allows 2.50 cubic inches per counted conductor at this size. Every conductor that originates outside a box and terminates or is spliced inside it counts once, each device yoke counts as two of the largest conductor in the box, and all the equipment grounding conductors together count as one. The total is compared against the box volume from Table 314.16(A). Table 314.16(B) stops at 6 AWG, so a larger conductor is sized by the pull and bend rules in 314.28 instead.
Where 10 AWG sits
| Conductor | 60°C | 75°C | 90°C |
|---|---|---|---|
| 12 AWG copper | 20 A | 25 A | 30 A |
| 10 AWG copper | 30 A | 35 A | 40 A |
| 8 AWG copper | 40 A | 50 A | 55 A |
10 AWG questions
- How many amps can 10 gauge wire handle?
- 10 AWG copper handles 30 A at 60°C, 35 A at 75°C, and 40 A at 90°C. The 60°C value is also the protection limit, because 240.4(D)(7) caps the device at 30 A after any correction and adjustment, so the higher columns are for derating rather than for a bigger breaker. Aluminum at the same size handles 25 A, 30 A, and 35 A.
- What size breaker for 10 gauge wire?
- 30 A. 240.4(D)(7) caps overcurrent protection at 30 A, and the cap applies after ambient correction and conductor adjustment. Aluminum takes 25 A at this size.
- What is 10 gauge wire used for?
- 30 A dryers, water heaters, and RV pedestals; 120/240 V appliance circuits that need a neutral; equipment grounding conductor on 30 A through 50 A circuits. Ten gauge carries 30 A at 60°C and is capped there by 240.4(D)(7), which makes it the standard dryer, water heater, and RV-pedestal conductor. 10/3 NM-B with ground is the four-wire cable a dryer or a range receptacle needs, and the same size feeds a 30 A pedestal or a small storage water heater that 422.13 treats as a continuous load.
- What size ground wire with 10 gauge conductors?
- 10 AWG copper is the equipment grounding conductor for 60 A circuits in Table 250.122, and 10 AWG aluminum is the ground for 20 A circuits. The ground is sized from the overcurrent device rather than from the phase conductors, and 250.122(B) raises it in the same proportion if the phase conductors are increased for voltage drop. It never has to be larger than the conductors it runs with.
- Is 10 AWG aluminum as good as copper?
- It carries less. In Table 310.16, 10 AWG aluminum is 25 A, 30 A, and 35 A against 30 A, 35 A, and 40 A for copper, so a load that copper serves at this size usually needs one size larger in aluminum. The lugs and devices it lands on have to be listed for aluminum conductors.