US (Inch) Screw Sizes with Decimal and Metric equivalents
It is very helpful to know the decimal equivalent for a US screw size you have. That is often found when trying to match a screw size using Digital Calipers (Inch Decimal to Screw Size) or drill a hole (Screw size to Nearest Fraction) for your project.
The second chart below is a US fraction to metric mm for the more common sizes up to 4".
US Screw size conversion chart:
Screw Size |
Inch Decimal |
Nearest Fraction |
Metric Equivalent |
#0 |
0.060 in. |
1/16" |
1.52 mm |
#1 |
0.073 in. |
5/64" |
1.85 mm |
#2 |
0.086 in. |
3/32" |
2.18 mm |
#3 |
0.099 in. |
7/64" |
2.51 mm |
#4 |
0.112 in. |
7/64" |
2.84 mm |
#5 |
0.125 in. |
1/8" |
3.18 mm |
#6 |
0.138 in. |
9/64" |
3.51 mm |
#8 |
0.164 in. |
5/32" |
4.17 mm |
#10 |
0.190 in. |
3/16" |
4.83 mm |
#12 |
0.216 in. |
7/32" |
5.49 mm |
#14 |
0.250 in. |
1/4" |
6.35 mm |
US Fraction to Metric mm equivalent chart:
US |
Metric |
Cont. US |
Cont. Metric |
|
1/16" |
1.59 mm |
1-3/8" |
34.93 mm |
|
1/8" |
3.18 mm |
1-1/2" |
38.10 mm |
|
3/16" |
4.76 mm |
1-5/8" |
41.28 mm |
|
1/4" |
6.35 mm |
1-3/4" |
44.45 mm |
|
5/16" |
7.94 mm |
1-7/8" |
47.63 mm |
|
3/8" |
9.53 mm |
2" |
50.80 mm |
|
7/16" |
11.11 mm |
2-1/4" |
57.15 mm |
|
1/2" |
12.70 mm |
2-1/2" |
63.50 mm |
|
9/16" |
14.29 mm |
2-3/4" |
69.85 mm |
|
5/8" |
15.88 mm |
3" |
76.20 mm |
|
11/16" |
17.46 mm |
3-1/4" |
82.55 mm |
|
3/4" |
19.05 mm |
3-1/2" |
88.90 mm |
|
7/8" |
22.23 mm |
3-3/4" |
95.25 mm |
|
1" |
25.40 mm |
4" |
101.6 mm |
|
1-1/4" |
31.75 mm |