Whitworth Size and Number Reference
You can use the table on this page to find the size of the Whitworth tool you need. Whitworth tools can be difficult to identify. For example a 1/4W wrench is the same as a 5/16BS, and is .525 inches across the flats, or 13.34mm. Please measure for your application before ordering Whitworth tools.
.
Diameter of Bolts
Width Across Flats
Whitworth
British
Standard
Inches
mm
8 BA N/A 0.152 3.86
7 BA N/A 0.172 4.37
6 BA N/A 0.193 4.90
5 BA N/A 0.220 5.59
4 BA N/A 0.248 6.30
1/16 W N/A 0.256 6.90
3 BA N/A 0.282 7.16
3/32 W N/A 0.297 7.54
2 BA N/A 0.324 8.23
1/8 W (3/16) 0.340 8.64
1 BA N/A 0.365 9.27
0 BA (7/32) 0.413 10.49
3/16 W 1/4 0.445 11.30
1/4 W 5/16 0.525 13.34
5/16 W 3/8 0.600 15.24
3/8 W 7/16 0.710 18.03
7/16 W 1/2 0.820 20.83
1/2 W 9/16 0.920 23.37
9/16 W 5/8 1.010 25.65
5/8 W (11/16) 1.100 27.94
11/16 W 3/4 1.200 30.48
3/4 W 7/8 1.300 33.02
13/16 W (15/16) 1.390 35.31
7/8 W 1. 1.480 37.59
1. W 1.1/8 1.670 42.42
1.1/8 W 1.1/4 1.860 47.24
1.1/4 W 1.3/8 2.050 52.07
1.3/8 W 1.1/2 2.220 56.39
1.1/2 W 1.5/8 2.410 61.21
1.5/8 W 1.3/4 2.580 65.35
1.3/4 W 2. 2.760 70.10
(1.7/8 W) N/A N/A 76.70
N/A 2.1/4 3.150 80.01
2. W N/A N/A N/A
N/A 2.1/2 3.550 90.17
N/A 2.3/4 3.890 98.81
N/A 3. 4.180 106.17
N/A 3.1/4 4.530 115.06
N/A 3.1/2 4.850 123.19
N/A 3.3/4 5.180 131.57
N/A 4. 5.550 140.97
N/A 4.1/2 6.380 162.05