Quit an inflated inch you have there. (must be American derived from US gallon)

1"=25mm is more like it.

Hello Hendrik

It depends what you mean by diameter. Metric pipe has OD as the nominal diameter. I have a (plastic) pipe catalogue that refers to DIN 8061/2 and DIN 8063. I think one of them is a dimensional standard but couldn't be sure from a quick google.

Metric pipe also has a NW figure, corresponding to nominal bore in inch systems. The actual bore of course varies with wall thickness (pipe class) as on inch systems.

Some examples are:-

ND 20mm, NW 15mm ~ 1/2"NB

ND 25mm, NW 20mm ~ 3/4"NB

ND 32mm, NW 25mm ~ 1"NB

ND 40mm, NW 32mm ~ 1-1/4"NB

I'm not sure whether steel pipe is also made to metric OD standards, perhaps somebody can comment?

Cheers.....Codey

I think posssibly he was regarding the outside diameter of the pipe. (tubing is measured from the outside). However pipe is measured from the inside diameter. Even though the outside remeains constant the inside changes according to schedual (wall thickness) (ie. scd 10,40,80 etc..) the nominal outside diameter of 3/4 pipe is 1.050 (closer to 26mm) Pipe scd and sizes for astm pipe can be found on pg 3 of any mcmaster carr catalog. I don't know about metric pipe so I can't help any further with that end. I hope this helps some.

How much research have you done?

What search engines have you used?

Please advise.

The sizes will not be the same diameter and the wall thicknesses will not be the same.

How many decimal places are you looking for?

Why?

I absolutely do not get your response to this post. It is completely pointless.

The OP has asked a question and clearly he/she needs this information so what does it matter to you why the OP needs it? Perhaps the OP wants to hang it on the wall, perhaps the OP needs it for a project, does it matter?

Because PWSlack wanted to make sure that it wasn't a homework question (at least, I assume). One of the few areas that CR4 does not want to go is as a place for students to have other engineers do their work for them.

Granted, the OP can lie and say whatever he or she wants in response to that question, but if you are going to do the work of answering, I think it is fair to at least ask what the info will be used for.

I think your confused by BSP / NPT pipe thread sizes which refer to the bore of the tube not the outside dia.

BSP

1/2" = 0.840" = 21.336 mm
3/4" = 1.050" = 26.67 mm etc etc


http://www.teamonslaught.fsnet.co.uk/threads.htm

Regards Woody

Hello woody,

I am not at all sure this request is not homework, in which case, and judging by the absolute guess the OP made as a comparison, I would not have given this info.

I simply worked all the various comparisons from the sizes in metric and Imperial out in my head. If someone is going to answer what is a very easily searched item the OP will learn nothing.

However you have decided to give the info' and have done a very good job of your research.

GA to you Sir!

It is common to identify pipes by inches using NPS or "Nominal Pipe Size". The metric equivalent is called DN or "diametre nominel". The metric designations conform to International Standards Organization (ISO) usage and apply to all plumbing, natural gas, heating oil, and miscellaneous piping used in buildings. The use of NPS does not conform to American Standard pipe designations where the term NPS means "National Pipe Thread Straight".

The above information is from the "Engineering ToolBox" website.

In a nutshell, pipe is measured ID with a schedule wall thickness so the outside gets bigger. Tube is measured OD with a measured wall thickness so the inside gets smaller.

So 1"nominal bore sched 40 has a wall thickness of 0.133" or 3.3782mm * 2 + 25.4 approx IC will be 32.1564mm using measurements or 1.315" on my chart. It usually works out somewhere in between. Pipe is never an absolute.

In a nutshell, pipe is measured ID with a schedule wall thickness so the outside gets bigger.

I think you better double check this, in the world i live in the inside gets smaller as the wall gets thicker

In a nutshell, pipe is measured ID with a schedule wall thickness so the outside gets bigger.

I think you better double check this, in the world i live in the inside gets smaller as the wall gets thicker

I don't know, if I'm working from a fixed id and the wall gets thicker then my outside gets bigger

If that's the case why do I buy flanges that are sized by schedule? Maybe because the wall thickness effect OD?

Your statement is incorrect. Originally, the nominal size was meant to be approximately the inside diameter on the thickest wall.

Then the OD was fixed for a given nominal size. No need to repeat as the actual dimensions are given above already. Then the various wall thickness for various pressures were established named schedules.

A 1/2" pipe is .840 inch OD (21.3 mm) and depending on the schedule the ID changes. Schedule 40 e.g has a wall thickness or .109, ID = .622" (15.8 mm), Sch. 160 z wall of .188, ID = .464" (11.8 mm), etc.

BTW, as far as I know there is no "Metric Pipe Specification" per se, only "metrified" Imperial pipe specifications.

Hi Floram,

The pipe sizes below are the ones I am most familiar with, though I have worked with a number of other types and sizes.

Please note the smaller sizes are in 'din' Metric sizes.

I realise 'pipe' covers a whole lot of types and uses but, I refer to these only. They are definitely sold in mm as, when the Metrication happened in the UK it was pretty hard to combine Metric and Imperial. Often it was easier to re-plumb the whole building to be sure of no leaks with dodgy pipe 'butts' and, where the pipe is connected to a tank for instance.

http://diydata.com/materials/copper_pipe/copper_pipe.php

-----------------------------------------------------------------------------

" Copper pipe is available in a number of sizes commonly:

• 8 and 10 mm - for use microbore central heating systems
• 12 and 15 mm - generally for connections to individual taps, appliances etc.
• 22, 28 and 35 mm - generally for long runs where use of 15 mm piping would cause excessive pressure drop.

Copper pipe is normally available in various lengths depending upon the type of stockist. Trade outlets may only stock 3 and 4 metre lengths whist small DIY outlets may hold sizes ranging from 1.5 to 2 metre.

'Old' imperial pipework

Copper pipework in older installations will probably be sized in imperial measurements - 1/2 inch, 3/4 inch, 1 inch etc. One point to bear in mind in the UK is that the measurement quoted for imperial sized pipe is the INNER diameter of the pipe whilst the measurement for metric pipes is the OUTER diameter - this means that the 1/2 inch pipe is very nearly identical to the 15 mm metric pipe. In fact these two sizes (1/2 inch and 15mm) can generally be joined using a 15 mm to 15mm connector.

The other imperial sizes do not have 'workable' equivalents metric sizes - joining these imperial to metric sized pipes require the use of adaptors specifically designed for the job (3/4 inch to 22mm, 1 inch to 22mm) - these adaptors are no more expensive than metric to metric connectors, they are just designed for the job. It does seem, however, that these adaptors are becoming less available; it's hard to find them on-line or at the major DIY stores, going to a 'proper' plumbers merchant probably gives the best chance for locating one. "

Take care.

Hello PP,

I like your explanation of DN etc, but I will be honest and tell you the figures in your chart are nowhere near close enough to be called "Nominal".

No insult intended OK?

The sizes where it is most likely to 'matter' are under an inch and you copy of these sizes were no where near, sorry.

Here is a more accurate size chart. The ".." after the numbers are the ones I have altered:

Sorry to say, but what you did was an approximate metric conversion to the inch dimensions.

The piping standard does not work this way, ok? Please don't spread false numbers.

Also no offense intended. But piping specs are different from your "assumption" of being a direct conversion.

Just like Hendrik above also "assumed" that pipe nominations are a direct conversion. Not so, the "Nominal" pipe sizes have been picked at a certain OD to reflect the ID size to be approximately that of the "nominal" designation at the thickest wall. The OD is does not change with the schedule but the ID does.

It is probably safe to say that you have not yet worked with pipes in your career.

Hello Floram,

Keep you hat on!

If you read the small amount of text in my post you refer to, I do not mention "PIPE" anywhere.

A previous post had obviously simply copied a chart from a site that converted inches to millimeters. I copies the same chart from that post and altered the figures to better approximate, in particular, the under an inch sizes, which were not near enough to be approx'.

That was all I did, nothing more, nothing less.

I realise with pipe the "1/2"" refers to the ID, and of course you need to allow for the thickness of the pipe material. This as you say gets thicker as pipe size increases to allow for any extra pressure in the larger pipe. I understand that, but others were doing a halfway decent job of explaining, or were in the process of doing do.

Take care and no insult intended OK?

Hello Baby Bear,

What you did was converting inch to metric. But that is way besides the point, and I trust that you agree.

You did not mention pipes alright but the heading does. We are taking piping here and the approximate conversions to metric from the pipe sizes that are given in inches.

You are talking apples we are talking oranges, or thus: you talk about math we are talking pipes.

Again, the nominal pipe diameter does not refer to the ID but to a selected OD that does not change for that size pipe, but the ID does with the wall thickness.

Again, I believe that you have not worked with pipes at all in your life. Likewise, I do not mean to offend you, just like set things straight.

Who knows, people might think you have invented a new piping standard. :) People read this and tend to believe it if they are not familiar with it, thinking of course that the writing knows his field. But you are not familiar with this field of pipe sizes. That is all I am trying to say.

Hello Floram,

I take on board what you are saying. But I originally did simply try to get PennPiper's post more accurate. Have you written to that post?

I have indeed worked will all kinds of plumbing pipe, that is copper, steel and plastic.

I have to admit though, I got my last explanation wrong, and for that I am sorry.

I am not in any way insulted my friend. I just hope I remember this for the 'next time!'

Take care.

Hello Baby Bear,

I see what you mean, you responded to PennPiper and not directly to the forum thread. In that sense I can see what you did, correcting him.

What pennPiper wrote was totally out as well and had nothing to do with pipe sizes. I wonder what his intentions were in writing that stuff.

Anyway, lets stay friends. Hopefully with PP too.

Hello Floram,

Hello Baby Bear,

I see what you mean, you responded to PennPiper and not directly to the forum thread. In that sense I can see what you did, correcting him.

What pennPiper wrote was totally out as well and had nothing to do with pipe sizes. I wonder what his intentions were in writing that stuff.

Anyway, lets stay friends. Hopefully with PP too.

-------------------------------------------------------------------------------------

I have nothing to be angry in any way with you Floram.

I accept I did make a mistake with the ID/OD thing, but, after your help I realised and understand for future ref', OK?

No problems my friend, Take care.

What I posted was NOT out of place with the OP.

AND

clearly in the post (at the top) is the following:

Nominal Pipe Size
NPS

(inches)

As you can see "PIPE" is indicated.

Also "the term "Nominal" does not mean "Actual"

Nominal means "In Name Only"

Hello PennPiper,

I do not want to get into an argument here. ....................

However, some of your sizing under one inch or (25.4 mm) was too far out, for me (at least) to consider it "Nominal". Some of those sizes when multiplied would come nowhere near what may be expected of the multiplied figure. You may not agree with it but it is my opinion only.If the multiplied figure was originally 1 mm out, then the product is going to be 1,2,3,4,5 mm or whatever the multiplier figure was. I consider the "Nominal" should be withing or as close to .5 mm when possible........... It is still nominal.

Take care my friend, and don't lets fall out over 1 mm?

Download the following file in PDF format for Table 1 (19 Pages) of ASME B36.10M for Welded and Seamless Wrought Steel Pipe ,which includes all data for all standard sizes of steel pipes in both Customary and SI Units: ASME_B3610M_-_2000__Table_1

Note. For stainless steel pipies there is another standard, ASME B36.19.

Refer to the following CR4 Thread: ASA Pipe Schedule.

Hello asherza,

Thank you for joining. We are a great lot of people and will offer help if you do not know or just get something wrong. Do not take it as an insult, it is just putting you back on the correct path, that is all. OK?

I understand you are asking for help but going by your figures (which are not correct) if ½" was your starting point. The series would go: 1/2" = 20 mm, 3/4" = 30 mm. Because, if 1/2 is 20, half of that number must be 30?

I am not very good at Math, but the problem you ask for help with, I worked out the 'ratio' of the smallest usually used Imperial size, 1/8" as the base.

Take an inch and divide it by 8. Your answer will be 1/8th or 1/8".

Multiply this, and your mm equivalent by 1/8", or 3 mm if you are working on the metric side.

The series runs like this:

[1/8" = 3 mm] [1/4" = 6 mm] [3/8" = 9 mm] [1/2" = 12 mm]

[5/8" = 15 mm] [3/4" = 18 mm] [7/8" = 21 mm] [1" = ~ 25 mm]

By the way, '~' means approximately, and is called a tild.

This is so basic, (if it wasn't I couldn't do it )

Get into Math, it is wonderful when you solve a problem like a ratio for instance!

Take care and search for a Math site right away! Or bury your head in a Math Tutorial Book.

Take care and good luck

I do not intend to mislead with any information about metric pipe How ever on pg 3 of every mcmaster carr catalog is a guide describing the "popular" industry standards for popular pipe sises and sceduals mcmaster.com There you will clearly see that All ASTM pipe is measured as a "trade size based roughly on the inside diameter. The outside is constant for threading and therefor the ID changes with wall thickness. (See pipe scheduals) I hope this helps out some.

Hello crimich13,

I hope you are well?

I thank you for the info. I have saved it though I do not have time at the moment to view it.

I always thought pipe was measured ID and 'Tube" was measured ex. But I excepted I was wrong as you will see from an earlier post of mine. You have put me right again, that I was correct in my thinking about pipe sizes, thank you.

Take care.

babybear:

Maybe this chart will help you to understand that for sizes 12" and smaller, the "Nominal" pipe size is NOT the actual pipe size. It is the pipe size "In Name Only" (Nominal).

For pipe sizes 14" and larger the Nominal pipe size is the actual outside diameter.

Note: All dimensions are in inches here.

Pipe Wall Thickness

Dimensions of Welded and Seamless Pipe Carbon,Alloy and Stainless Steel
ANSI B36.10,B36.19

Hello PennPiper,

Hope you are fine?

I have worked with pipe as in plumbing and conduit type pipes or the conduit may be classed as a 'tube', for a good section of my life off and on. I never really thought or needed to think or worry about the actual flow amount through the pipe, just asked for 12 mm, 18 mm, 25 mm, etc?

I thank you for taking the time to reply post to me with the chart which I have yet to view properly, thanks once again.I do hope that you took the discussion as a whole as a 'professional' one and did not mind me highlighting your name to another poster? I cannot recall whom it was now, but they have their idea and I and you and at least one other have ours!

I take everyone as I 'hear' them and try to keep the discussion sensible because you never know where it may end and that person whom you may have thought 'rubbed you slightly the wrong way', in a nice way usually, will come to be your friend and you just may come to rely on each other to some extent, you just never know?

No one did it on this thread but, sometimes there if 'street language' which creeps in when someone makes an observation the other person did not like, although they may well of been telling the truth and stating a fact. Some people just want, and 'think' they know it all. This is not a social Networking Site per se, it is a meeting place for like minded sensible people, as much as a place where anyone can ask a sensible request and get a sensible and maybe after some friendly banter get a correct answer, nothing more or less.

The real world is not like that and neither are the Members on this site. All pretty much expert in there own and often several other 'fields', so any kind of unprofessional 'speak', is usually jumped on and stopped.[p]Now I am not saying this because I think you or anyone on this thread is like that, but you have to just go with the flow and if you you or I read something a certain way and we mention it here, it remains to be seen if, in fact what we think of as true is a fact? I am going the long way about saying thank you for being a 'gent', (if that's what you are?.......................

I hope you do not mind or the rest of the thread does not mind this long post?

Take care my friends, bb

BabyBear,

Go here for a detailed "Inch to Metric" Pipe Chart.

http://www.maselmon.com/Content.aspx?ContentID=24

Hello PennPiper, I thank you for your reply post............

I thank you for the site. I will keep it for ref, but personally I do not need it. I will however keep it to use for CR4.

I have no problems with conversion from Metric to Imperial at all. I do these conversion automatically both from Metric to Imperial and the reverse.

I have not had time yet but will look for confirmation that it is the ID of pipe which is measured. I got pretty deep into this about a year ago on this site and got to know the wall thickness' also. But since have not held it in my mind.

A Member 'gsuhas' both criticised and helped me with that criticism with ref' to figuring out the 'area' and volume of a pipe, I am talking of the very large size pipe used for waterworks and sewage plants.

These kinds of questions of pipe area and volume and flow come up now and then but, as I do not work with such pipes now, I do not have there specs to hand?

Take care my friend and I thank you for your support.

PS. Please forgive any spelling mistakes, as I had to reply and replied on a Browser which does not have a spell checker.

Asherza:

Go here for a detailed "Inch to Metric" Pipe Chart.

http://www.maselmon.com/Content.aspx?ContentID=24

ID 1/8 or 6mm OD 10.3 Wall 1.24/1.73/2.41

My question is from the table taken from the above link, how, with an increasing wall thickness does ID & OD stay the same?