Terminal Torque & Tightening Lookup

Look up electrical termination torque values (lb-in, lb-ft, N·m) for lugs, breakers, and screws per NEC §110.14(D) & Table 110.14(D).

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⚡ Test your knowledge
NEC Article 220 was renumbered in the 2026 code cycle. What is the new article number?
  • A. Art. 100
  • B. Art. 120
  • C. Art. 200
  • D. Art. 230
💡 NEC 2026 renumbered Article 220 (Branch-Circuit, Feeder, and Service Calculations) to Article 120.
Energy Management Systems were moved from Article 750 to which article in NEC 2026?
  • A. Art. 100
  • B. Art. 125
  • C. Art. 130
  • D. Art. 150
💡 NEC 2026 moved Energy Management Systems from Article 750 to Article 130.
Which NEC standard size overcurrent device comes after 90A?
  • A. 95A
  • B. 100A
  • C. 110A
  • D. 105A
💡 Per NEC §240.6(A), the standard sizes are …90, 100, 110, 125… There is no 95A standard size.

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How it works & the NEC rules behind it

Improperly torqued electrical connections are among the leading causes of electrical fires, hot spots, and equipment failures. Under NEC §110.14(D), tightening torque values for terminal connections must be achieved using a calibrated torque tool (torque wrench or calibrated torque screwdriver).

Core Code Requirements (NEC §110.14(D)):

  • 1. Manufacturer Instructions First (§110.3(B) / §110.14(D)): Where tightening torque is indicated by the manufacturer on the equipment label or instructions, those values are mandatory.
  • 2. NEC Default Table 110.14(D): Where manufacturer torque values are missing or unreadable in the field, the default values in Table 110.14(D) must be applied.
  • 3. Calibrated Tool Mandatory: Hand-tightening by feel or "snug plus a quarter turn" is a code violation. An inspector may request verification of calibrated torque tool usage.
  • 4. Torque Units Conversion:
    • 1 Foot-Pound (lb-ft) = 12 Inch-Pounds (lb-in)
    • 1 Newton-Meter (N·m) ≈ 8.85 Inch-Pounds (lb-in)

Formulas & equations

Torque in lb-ft = Torque in lb-in ÷ 12 Torque in Newton-Meters (N·m) = Torque in lb-in × 0.1130 Mandatory Calibrated Torque Tool Usage (§110.14(D))

NEC reference table

Screw / Terminal Type Socket Size / Conductor Torque (Pound-Inches) Torque (Pound-Feet / N·m)
15A – 30A Circuit Breaker (Slotted)#14 – #10 AWG20 – 35 lb-in1.7 – 2.9 lb-ft (2.3 – 4.0 N·m)
40A – 60A Circuit Breaker (Slotted/Hex)#8 – #4 AWG40 – 45 lb-in3.3 – 3.75 lb-ft (4.5 – 5.1 N·m)
70A – 100A Breaker / Mechanical Lug#3 – #1/0 AWG50 – 75 lb-in4.2 – 6.25 lb-ft (5.6 – 8.5 N·m)
125A – 225A Panel Main Lug (Hex)5/16" Hex / 250 kcmil250 – 275 lb-in20.8 – 22.9 lb-ft (28 – 31 N·m)
400A Main Switch Lug (Hex)3/8" Hex / 500 kcmil375 lb-in31.25 lb-ft (42.4 N·m)
800A Switchboard Bus Lug (Hex)1/2" Hex / 750 kcmil500 lb-in41.67 lb-ft (56.5 N·m)

*Source: NEC Table 110.14(D) (Tightening Torque for Screws & Connectors).

Worked example, step by step

Example: Torquing 200A Panelboard Main Lugs (250 kcmil with 5/16" Hex Socket)

Connection: 200A Main Breaker mechanical aluminum lug with 5/16" internal hex socket.

  • 1. Identification: Internal hex-head socket screw, 5/16" across flats.
  • 2. Table 110.14(D) Lookup: 5/16" Hex Socket = 275 lb-in (Pound-Inches).
  • 3. Conversion to Foot-Pounds: 275 ÷ 12 = 22.9 lb-ft.
  • 4. Conversion to Newton-Meters: 275 × 0.113 = 31.1 N·m.
  • 5. Verification: Apply calibrated torque wrench with 5/16" hex bit until the click is achieved.

Frequently asked questions

YES. If the manufacturer of the receptacle or switch specifies a tightening torque on the box packaging or device body (typically 12 to 14 lb-in for terminal screws), a calibrated torque screwdriver is required to tighten those screws to code.

Over-tightening strips aluminum threads, shears copper conductor strands, and induces excessive mechanical stress that leads to metal fatigue, loose connections over thermal cycles, and eventual arcing faults.

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