What size wrench or spanner fits 7/8 in?

7/8 in bolt uses a 1-5/16 wrench or spanner, measured across the flats of the hex head.

What is the torque for 7/8 in?

A typical tightening torque for 7/8 in bolt in Grade 5 on dry threads is about 550 Nm (405.9 ft·lb). Always confirm against the manufacturer spec for important joints.

What thread pitch and tap drill does 7/8 in use?

7/8 in bolt has a thread pitch of 9 TPI (threads per inch) and uses a 49/64 (19.4 mm) tap drill, with a 15/16 clearance hole.

What is 7/8 in used for?

7/8 in is commonly used in heavy structural, industrial, marine. It is one of the most popular sizes in its category.

What is the closest metric size to 7/8 in?

The closest metric size to 7/8 in is approximately ~M22, though they are not exactly interchangeable.

Home › Imperial / SAE Bolts › 7/8 in

7/8 in bolt size

1-5/16 wrench

across-flats spanner / socket size for 7/8 in

7/8 in bolt — Heavy structural, industrial, marine.

Full specification

System	Imperial UNC
Nominal diameter	7/8 in (0.875 in / 22.23 mm)
Thread pitch	9 TPI
Wrench / spanner (across flats)	1-5/16
Tap drill	49/64 (19.4 mm)
Clearance hole	15/16
Common grade / class	Grade 5
Typical torque	550 Nm (405.9 ft·lb)
Closest other-system size	~M22

🔧 Torque unit converter

Newton-metres (Nm) Foot-pounds (ft·lb) Inch-pounds (in·lb)

Pre-filled with the typical torque for 7/8 in (Grade 5, dry). Edit any field to convert.

⚠️ Torque values here are general references for Grade 5 on clean, dry threads. Lubrication, coatings, and the joint material change the figure significantly. For structural, automotive, or safety-critical work, always use the torque specified by the manufacturer or engineer.

About 7/8 in

Heavy structural, industrial, marine.

A 49/64 drill is the standard tap drill for 7/8 in-9 UNC thread. The standard clearance hole is 15/16.

7/8 in is part of the Unified National Coarse (UNC) thread series, defined in ASME B1.1. The wrench size 1-5/16 is measured across the flats of the hex head.

Common applications

7/8 in bolts are widely used in:

Heavy structural, industrial, marine
General machinery and equipment assembly
Automotive components and repairs
Structural connections (when specified by engineer)
Industrial maintenance and repair

Material and grade information

The typical grade for 7/8 in is Grade 5. This indicates:

Grade 5: Medium carbon steel, quenched and tempered
Tensile strength: 120,000 PSI
Yield strength: 92,000 PSI
Common coatings: Zinc plated, hot-dip galvanized, or plain

Frequently asked questions

What size wrench or spanner fits 7/8 in?: 7/8 in bolt uses a 1-5/16 wrench or spanner, measured across the flats of the hex head.
What is the torque for 7/8 in?: A typical tightening torque for 7/8 in bolt in Grade 5 on dry threads is about 550 Nm (405.9 ft·lb). Always confirm against the manufacturer spec for important joints.
What thread pitch and tap drill does 7/8 in use?: 7/8 in bolt has a thread pitch of 9 TPI (threads per inch) and uses a 49/64 (19.4 mm) tap drill, with a 15/16 clearance hole.
What is 7/8 in used for?: 7/8 in is commonly used in heavy structural, industrial, marine. It is one of the most popular sizes in its category.
What is the closest metric size to 7/8 in?: The closest metric size to 7/8 in is approximately ~M22, though they are not exactly interchangeable.