Inch size	Commonly known as inch size * 1	Flange size	Nominal caliber [mm]	Outer diameter [mm]	Approximate inner diameter [mm]
1/8B	1 minute [Ichibu]	–	6A	10.5	6.5
1/4B	2 minutes [nibu]	–	8A	13.8	9.2
3/8B	3 minutes [sanbu]	10A	10A	17.3	12.7
1/2B	4 minutes [Yonbu]	15A	15A	21.7	16.1
3/4B	6 minutes [Rokubu]	20A	20A	27.2	21.6
1B	inch	25A	25A	34.0	27.6
1 1/4B	Inch 2 minutes [inch nibu]	32A	32A	42.7	35.7
1 1/2B	Inch _and a half [inch]	40A	40A	48.6	41.6
2B	2 inches [in inches]	50A	50A	60.5	52.9
2 1/2B	Two _and a half inches	65A	65A	76.3	67.9
3B	3 inches [san inches]	80A	80A	89.1	80.7
4B	4 inches [4 inches]	100A	100A	114.3	105.3
5B	5 inches [go inches]	125A	125A	139.8	130.8
6B	6 inches [6 inches]	150A	150A	165.2	155.2
8B	8 inches [Hachi inches]	200A	200A	216.3	204.7

* 1 Inch piping diameter is expressed when the denominator is 8, for example, 1/2^B becomes 4/8^B, _and the numerator is taken. Say 4 minutes.