NEC electrical tables and calculators, without the page-flipping
Conduit fill, wire ampacity, derating, box fill, grounding, motor currents and voltage drop — fast, mobile-friendly and free. Built for electricians, engineers, inspectors and students.
Conduit fill calculatorAmpacity Table 310.16Tables and tools
Conduit fill chart & calculator
How many wires fit in EMT, PVC, rigid, IMC and flex. Mixed wire sizes supported.
Article 310Wire ampacity charts
Tables 310.16 through 310.19 for copper and aluminum at 60, 75 and 90°C.
310.15Derating factors
Ambient temperature correction and adjustment for more than three conductors.
CalculatorVoltage drop calculator
Drop in volts and percent, with the wire size needed to stay under 3%.
314.16Box fill calculator
Required box volume from conductors, devices, clamps and grounds.
250.122 · 250.66Grounding conductor size
Equipment ground size by breaker rating; electrode conductor by service size.
430.247–250Motor full-load amps
FLA by horsepower and voltage, with wire, breaker and fuse sizing.
200.6 · 250.119Wire color codes
What the code requires and what the trade uses at 120/208/240 V and 277/480 V.
14 AWG – 1000 kcmilWire size pages
Ampacity, fill, dimensions and resistance for each conductor size.
Common lookups
| Question | Answer |
|---|---|
| How many #12 wires in 1/2" EMT? | 9 THHN |
| How many #12 wires in 3/4" EMT? | 16 THHN |
| How many #10 wires in 3/4" PVC? | 9 THHN |
| Ampacity of 6 AWG copper? | 65 A at 75°C |
| Wire for a 200 A service? | 2/0 Cu or 4/0 Al (dwelling) |
| Ground wire for a 100 A breaker? | 8 AWG Cu / 6 AWG Al |
| 5 HP motor at 230 V 3-phase? | 15.2 A |
| Box volume per #12 conductor? | 2.25 in³ |
Conduit fill by raceway type
- EMT
- PVC Schedule 40
- PVC Schedule 80
- Rigid Metal Conduit
- IMC
- Flexible Metal Conduit
- Liquidtight Flexible Metal Conduit
- ENT
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
About this reference
NECTables presents the engineering data electricians look up every day in a form that works on a phone in a crawl space. Conductor counts are calculated here from conduit and wire dimensions using the Chapter 9 fill rules; ampacity, grounding and motor values are the commonly published figures that appear on manufacturer charts and in the 2023 edition of NFPA 70. The site is a companion to the code book, not a replacement for it. More about our sources and method.
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.