1000 kcmil Wire — Ampacity, Conduit Fill & Dimensions
Everything the code tables say about 1000 kcmil conductors on one page: ampacity by temperature rating, breaker limits, conduit fill, physical size, resistance and voltage-drop distances.
1000 kcmil copper carries 455 A at 60°C, 545 A at 75°C and 615 A at 90°C.
1000 kcmil ampacity
| Copper | Aluminum | |||||
|---|---|---|---|---|---|---|
| Installation | 60°C | 75°C | 90°C | 60°C | 75°C | 90°C |
| Raceway, cable or earth — Table 310.16 | 455 | 545 | 615 | 375 | 445 | 500 |
| Single conductor in free air — Table 310.17 | 780 | 935 | 1055 | 625 | 750 | 845 |
Typical use: 545 A copper. Very stiff; parallel smaller sets are nearly always cheaper and easier to pull.
Use the column that matches the lowest temperature rating in the circuit — usually the 75°C terminations on breakers and lugs. The 90°C column is a starting point for derating, not a rating you can load the wire to. NM-B (Romex) cable is always limited to the 60°C column.
1000 kcmil conduit fill
| Conduit | 1/2" | 3/4" | 1" | 1-1/4" | 1-1/2" | 2" | 2-1/2" | 3" | 4" |
|---|---|---|---|---|---|---|---|---|---|
| EMT | — | — | — | — | — | 1 | 1 | 2 | 4 |
| PVC Schedule 40 | — | — | — | — | — | 1 | 1 | 1 | 3 |
| PVC Schedule 80 | — | — | — | — | — | 1 | 1 | 1 | 3 |
| Rigid Metal Conduit | — | — | — | — | — | 1 | 1 | 1 | 4 |
| IMC | — | — | — | — | — | 1 | 1 | 1 | 4 |
| Flexible Metal Conduit | — | — | — | — | — | 1 | 1 | 1 | 3 |
| Liquidtight Flexible Metal Conduit | — | — | — | — | — | 1 | 1 | 1 | 3 |
| ENT | — | — | — | — | — | 1 | — | — | — |
Mixing sizes or using another insulation? Use the conduit fill calculator.
1000 kcmil dimensions
| Insulation | Diameter (in) | Diameter (mm) | Area (in²) | Area (mm²) |
|---|---|---|---|---|
| THHN, THWN, THWN-2 | 1.317 | 33.45 | 1.3478 | 869.5 |
| XHHW, XHHW-2, XHH | 1.312 | 33.32 | 1.3519 | 872.2 |
| TW, THW, THHW, THW-2 | 1.372 | 34.85 | 1.4784 | 953.8 |
| RHH, RHW, RHW-2 (with outer covering) | 1.502 | 38.15 | 1.7719 | 1143.2 |
1000 kcmil voltage drop
| Load | 120 V 1-phase | 240 V 1-phase | 208 V 3-phase | 480 V 3-phase |
|---|---|---|---|---|
| 200 A | 697 ft | 1395 ft | 1396 ft | 3222 ft |
| 250 A | 558 ft | 1116 ft | 1117 ft | 2577 ft |
| 300 A | 465 ft | 930 ft | 930 ft | 2148 ft |
| 400 A | 348 ft | 697 ft | 698 ft | 1611 ft |
| 500 A | 279 ft | 558 ft | 558 ft | 1288 ft |
Based on 0.0129 Ω per 1000 ft for stranded copper at 75°C (0.0212 Ω for aluminum). For other loads and lengths use the voltage drop calculator.
All wire sizes
- 14 AWG
- 12 AWG
- 10 AWG
- 8 AWG
- 6 AWG
- 4 AWG
- 3 AWG
- 2 AWG
- 1 AWG
- 1/0 AWG
- 2/0 AWG
- 3/0 AWG
- 4/0 AWG
- 250 kcmil
- 300 kcmil
- 350 kcmil
- 400 kcmil
- 500 kcmil
- 600 kcmil
- 700 kcmil
- 750 kcmil
- 800 kcmil
- 900 kcmil
- 1000 kcmil
Frequently asked questions
How many amps can 1000 kcmil wire carry?
1000 kcmil copper is rated 455 A at 60°C, 545 A at 75°C and 615 A at 90°C when run in conduit or cable. Aluminum is rated 375, 445 and 500 A. Most terminations are rated 75°C, so the 75°C figure is the one normally used.
What size conduit do I need for 1000 kcmil wire?
Three 1000 kcmil THHN conductors need at least 3-1/2-inch EMT. Add the ground wire’s area and check the chart above for larger bundles.
What is the diameter of 1000 kcmil wire?
The bare conductor is 1,000,000 circular mils (506.7 mm²). With THHN insulation the overall diameter is about 1.317 in (33.45 mm) and the area is 1.3478 in², which is the figure used for conduit fill.
How far can I run 1000 kcmil wire?
For a 3% voltage drop on a 240 V single-phase circuit carrying 500 A, about 558 feet one way in copper. Halve that at 120 V. Lighter loads go proportionally farther.
NECTables.com is an independent reference and is not affiliated with, endorsed by, or a substitute for the National Fire Protection Association (NFPA). NEC® and National Electrical Code® are registered trademarks of the NFPA. Values shown are commonly published engineering data and independent calculations based on the methods of NFPA 70; they are not a reproduction of the Code. Always confirm against the edition adopted in your jurisdiction, including local amendments, and consult a licensed electrician or engineer before doing electrical work.