Screw Size Converter

Compare screw gauge sizes, machine screw sizes, metric screw sizes, decimal inches, millimeters, thread pitch, and threads per inch for construction, woodworking, hardware, and repair projects.

Convert Screw Size

#8 screw = 0.164 in diameter
Your screw size result will appear here.

Common screw size references

#6 screw diameter:
0.138 in / 3.505 mm

#8 screw diameter:
0.164 in / 4.166 mm

#10 screw diameter:
0.190 in / 4.826 mm

M6 screw diameter:
6 mm / 0.236 in

Where screw size conversions are used

Screw size conversions are useful for wood screws, deck screws, drywall screws, machine screws, sheet metal screws, cabinet screws, anchors, pilot holes, hardware matching, and construction repair work.

Use this converter when comparing screw gauge, metric M sizes, decimal inches, millimeters, thread pitch, and screw diameter references.

What your screw size result means

Your result shows the selected screw size converted into decimal inches, millimeters, centimeters, approximate nearest fractional inch, and thread reference information.

Screw fit depends on major diameter, thread pitch, thread form, screw length, head style, pilot hole size, material, and manufacturer tolerances. Always verify final sizing for structural, mechanical, or code-sensitive work.

Screw size converter tips

Frequently asked questions

What diameter is a #8 screw?

A common #8 screw has a major diameter of about 0.164 inches, or about 4.166 millimeters.

What diameter is a #10 screw?

A common #10 screw has a major diameter of about 0.190 inches, or about 4.826 millimeters.

Is M6 the same as 1/4 inch?

No. M6 is 6 mm in diameter, while 1/4 inch is 6.35 mm. They are close, but they are not the same size.

What does 8-32 mean?

8-32 is a machine screw size. The 8 is the screw size number, and 32 means 32 threads per inch.

Does this converter choose the right pilot hole?

No. This converter compares screw diameters. Pilot hole size depends on screw type, thread design, material, and whether the hole is clearance, tap, or pilot.