Snap diameter to standard nominal size

Description

Converts an input diameter to the corresponding standard nominal size based on a pipe reference table.

The calculation compares the input diameter against tabulated outside diameter $OD$ values and selects the row with the smallest absolute difference. It then returns the associated DN and NPS values.

There are 2 calculation options:

Single value
Series of values

This tool is useful for matching calculated or specified diameters to standardized nominal sizes used in engineering design, specifications, and component selection.

Adjustment criterion

The input diameter $D_{in}$ is compared against the reference outside diameter values $OD_i$ in the table. For each row $i$ , the following is evaluated:

\Delta_i = \left| D_{in} - OD_i \right|

The selected row is the one that minimizes this difference:

i^* = \arg\min_i \left| D_{in} - OD_i \right|

The outputs are then taken directly from the selected row:

DN = DN_{i^*}

NPS = NPS_{i^*}

Note: the snapping is based on the reference outside diameter $OD$ , not on direct rounding of the $DN$ value.

Reference table used

DN (mm)	NPS (in)	OD (mm)
6	1/8	10.3
8	1/4	13.7
10	3/8	17.1
15	1/2	21.3
20	3/4	26.7
25	1	33.4
32	1 1/4	42.2
40	1 1/2	48.3
50	2	60.3
65	2 1/2	73.0
80	3	88.9
90	3 1/2	101.6
100	4	114.3
125	5	141.3
150	6	168.3
200	8	219.1
250	10	273.0
300	12	323.9
350	14	355.6
400	16	406.4
450	18	457.2
500	20	508.0
600	24	609.6
700	28	711.2
750	30	762.0
800	32	812.8
900	36	914.4
1000	40	1016.0
1050	42	1066.8
1200	48	1219.2

Reference: table based on ASME B36.10M / ISO 4200.

Calculation method: Single value

Input data

Parameter	Default units	Description
Input diameter $D_{in}$	mm	Diameter provided by the user, to be adjusted to the nearest standard nominal size based on the reference outside diameter.

Output data

Parameter	Default units	Description
Nominal diameter $DN$	mm	Standard nominal size corresponding to the selected row in the reference table.
Nominal pipe size $NPS$	in	NPS designation corresponding to the selected row in the reference table.

Calculation method: Series of values

Input data

Parameter	Default units	Description
Input diameter $D_{in}$	mm	Series of diameters provided by the user for batch adjustment to standard nominal sizes.

Output data

Parameter	Default units	Description
Nominal diameter $DN$	mm	Series of standard nominal sizes obtained from the reference table.
Nominal pipe size $NPS$	in	Series of corresponding NPS designations.

Calculations

Snap Diameter to Standard Size

Input data

Output data

Input data

Raw value

Output data

Standard value

Standard NPS value

Description

Adjustment criterion

Reference table used

Calculation method: Single value

Input data

Output data

Calculation method: Series of values

Input data

Output data