Threads & Spanner Sizes
BSP(Britsih Standard Pipe)
BSP sizes were originally based on the inner diameter (measured in inches) of a steel tube for which the thread was intended.
BSP causes some confusion when it comes to sizing if you are not sure, please refer to the additional info for more help.
BSP TPI Ext Dia-mm
Nuts & Bolts - Spanner Sizes
Thread Spanner Thread Spanner
4mm 7mm 3/16" 3/8"
5mm 8mm 1/4" 7/16"
6mm 10mm 5/16" 1/2"
7mm 11mm 3/8" 9/16"
8mm 13mm 7/16" 5/8"
10mm 17mm 1/2" 3/4"
12mm 19mm 9/16" 1"
14mm 22mm 3/4" 1.1/8"
16mm 24mm
20mm 30mm
Japanese
Thread Spanner
4mm 7mm
5mm 8mm
6mm 10mm
5mm 8mm
6mm 10mm
8mm 12mm
10mm 14mm
12mm 17mm
14mm 19mm
16mm 22mm