Inch size	Commonly known as inch size * 2	Flange size	Nominal caliber [mm]	Outer diameter [mm]	Approximate inner diameter [mm]
1/8B	1 minute [Ichibu]	–	–	–	–
1/4B	2 minutes [nibu]	–	–	–	–
3/8B	3 minutes [sanbu]	–	–	–	–
1/2B	4 minutes [Yonbu]	13A	13A ※2	18.0	13.0
		15A	16A ※2	22.0	16.0
3/4B	6 minutes [Rokubu]	20A	20A	26.0	20.0
1B	inch	25A	25A	32.0	25.0
1 1/4B	Inch 2 minutes [inch nibu]	32A	30A ※2	38.0	31.0
1 1/2B	Inch _and a half [inch]	40A	40A	48.0	40.0
2B	2 inches [in inches]	50A	50A	60.0	51.0
2 1/2B	Two _and a half inches	–	–	–	–
3B	3 inches [san inches]	80A	75A ※2	89.0	77.2
4B	4 inches [4 inches]	100A	100A	114.0	99.8
5B	5 inches [go inches]	–	–	–	–
6B	6 inches [6 inches]	150A	150A	165.0	145.8
8B	8 inches [Hachi inches]	–	–	–	–

* When the denominator is 8 for the pipe diameter expressed in 1 inch, for example, 1 / 2B becomes 4 / 8B, _and the numerator is called 4 minutes.
* 2 The nominal diameter is different from SGP.