How do I know my Allen key bolt size?

Most Allen wrenches have the size stamped clearly on the side of the tiny, angled tool. The inch or millimeter size may have rubbed off with use or may be entirely too small to read. In this case, an Allen wrench or hex key chart can make finding the right size for your socket head much easier.

What size allen key fits a M6 bolt?

Metric Allen Key Table

Socket Shoulder Screw Key Size
8 (M6) 4mm
10 (M8) 5mm
12 (M10) 6mm
16 (M12) 8mm

What is a standard size Allen key?

Hex key sizes

6mm (or 7/32 inch) Allen key 8mm (or 5/16 inch) Allen key 10mm (or 3/8 inch) Allen key
Shop for individual and sets including 6mm Allen keys Shop for individual and sets including 8mm Allen keys Shop for individual and sets including 10mm Allen keys

What size is Allen bolt?

Drive Sizes for US Allen Drive Screws

Screw Diameter Drive Size
Socket Flat Socket Button
#0 0.89mm (0.035″) 0.89mm (0.035″)
#1 1.27mm (0.050″) 1.27mm (0.050″)
#2 1.27mm (0.050″) 1.27mm (0.050″)

What is the most common Allen key size?

In standard measurements, the most common Allen wrench sizes for the tasks listed above (that is, automotive repair, bike work and furniture assembly) are the 5/32-inch, 3/16-inch and ¼-inch sizes.

What size bolt does a 9/16 wrench fit?

Hex Bolt, Lag Bolt, Square Bolt and Heavy Hex Bolt

US Bolts
Bolt Diameter (in) Head and Wrench Size (in)
1/2 3/4 7/8
9/16 13/16
5/8 15/16 1 1/16

What size head is a M8 bolt?


Size Diameter Head Diameter
M4-0.7 4.00 7.00
M5-0.8 5.00 8.50
M6-1.0 6.00 10.00
M8-1.25 8.00 13.00

What size is a #5 Allen key?

SAE Substitutes for MM

Imperial Hex Key Metric Hex Size
3/16″ 5 mm
7/32″ 5.5 mm & 6 mm
1/4″ 7 mm
5/16 “ 8 mm

Which is Allen key should I use for the socket screw I am using?

We are often asked what size hex Allen key wrench will fit a certain socket screw. Below is a conversion chart to help:

What are the dimensions of an allen key?

These dimensions of allen keys can be used to check the accessibility of your bolts were space is limited. For example for an M8 socket head cap screw we need at least 32+8(head size) = 40mm clearance above the screw for easy accessibility.

Can a hex key be used with an allen wrench?

Hold on to it or post it somewhere in the garage where you can hold up the key or socket screw head to the physical picture. This can help you to determine which size of Allen wrench you need or have on hand. While Allen wrenches and hex keys seem durable enough, they can cause damage if you use the wrong size on a socket screw head.

How big is a SAE key to an allen wrench?

Moving over to the right-hand side, we’ve provided the metric to SAE guide for Allen wrench conversions. Similar to the metric hex keys, the SAE hex wrenches don’t always have a perfect substitute as seen for SAE size 3/16″.