Imperial / SAE Bolts — Complete Size Reference
Complete reference for imperial UNC bolts from #8 to 1 inch. Wrench sizes, thread pitch (TPI), tap drills, torque specifications, and applications.
#8-3211/32 wrench · 32 TPI · 3.5 Nm#10-243/8 wrench · 24 TPI · 5.5 Nm#12-247/16 wrench · 24 TPI · 8 Nm1/4 in7/16 wrench · 20 TPI · 12 Nm5/16 in1/2 wrench · 18 TPI · 22 Nm3/8 in9/16 wrench · 16 TPI · 47 Nm7/16 in5/8 wrench · 14 TPI · 70 Nm1/2 in3/4 wrench · 13 TPI · 110 Nm9/16 in13/16 wrench · 12 TPI · 150 Nm5/8 in15/16 wrench · 11 TPI · 210 Nm3/4 in1-1/8 wrench · 10 TPI · 350 Nm7/8 in1-5/16 wrench · 9 TPI · 550 Nm1 in1-1/2 wrench · 8 TPI · 800 Nm
About imperial bolts
Imperial bolts (also called SAE bolts) are designated by their nominal diameter in inches or number sizes. The most common thread type is UNC (Unified National Coarse).
Imperial bolt designation
Imperial bolts are designated as: [diameter]-[TPI]
- 1/4-20 = 1/4 inch diameter with 20 threads per inch
- 3/8-16 = 3/8 inch diameter with 16 threads per inch
- #10-24 = #10 size (0.190 inch) with 24 threads per inch
Number sizes vs fractional sizes
Small imperial bolts use number sizes (#0 to #12), while larger bolts use fractional inch sizes (1/4 inch and up).
SAE bolt grades
Imperial bolts are graded by SAE grade:
- Grade 2: Low carbon steel, low/medium strength
- Grade 5: Medium carbon steel, quenched and tempered (most common)
- Grade 8: Alloy steel, quenched and tempered (high strength)