What’s the difference, and when are they used?

Let’s start with a couple of definitions found with a web search.

Definition used by the ISA (International Society of Automation):

A Material Take Off (MTO) is the process of analysing the drawings and determining all the materials required to accomplish the design. We then use the material takeoff to create a bill of materials (BOM). Inspection does not aid in creating a bill of materials. Procurement and requisition are activities that occur after the bill of materials is complete.  

From Wikipedia (

A bill of quantities (BOQ) is a document used in tendering in the construction industry in which materials, parts, and labour (and their costs) are itemized. It also (ideally) details the terms and conditions of the construction or repair contract and itemizes all work to enable a contractor to price the work for which he or she is bidding.

What does this mean in terms of Piping Design, and what does it mean to the piping designer?

Material Take Off (MTO)

The piping MTO is a list of all piping items required to purchase, fabricate and construct the design. This list will contain all piping items, pipe, fittings, flanges, gaskets, bolts, nuts, elbows, reducers, tees, valves, speciality items etc. Everything must be accounted for.  

Bill Of Materials (BOM)

In the piping world, the Bill of Materials (BOM) usually appears on a Piping Isometric drawing.
The BOM will list all the components required to fabricate and construct the line shown on that particular drawing.
The piping BOM is not used for purchasing. The piping and components will have already been purchased and are readily available to the fabricator, who builds the line from the materials / components specified on the BOM.  

Bill Of Quantities (BOQ)

The piping Bill of Quantities (BOQ) is a tendering document. This would cover the scope of materials for the entire piping component of the project, but it would not be the final, definitive list.
This is produced earlier in the project, prior to Construction level drawings, so it would not have the definition that the MTO gives.

MTO Stages

Depending on the project, there are typically three material take-off exercises during a process piping  project. Preliminary, Secondary and Final.
There may be more, and they may have different names, and may occur at different phases of the project -  e.g. Preliminary, 30%, 50%, 70%, 90%, Final etc.

Preliminary MTO:

The preliminary piping MTO is done very early in the design process.
There is usually limited information to work with, and development is at an early stage.
This would never be used for purchasing reasons.

There are 2 reasons a preliminary piping MTO is usually done.

  • Assist with the early "order-of-magnitude" (+/- 10%) estimate for the overall project.
  • To issue early order of magnitude "RFQ's" (Request for Quote) for piping materials.

The preliminary piping MTO is only done, once the P&ID (s) are ready for Client Review and Approval and a Plot Plan has been "Approved" by the Client or has been issued to the client for approval.
Normally, detailed design has not started.

The preliminary piping MTO should be undertaken by an experienced senior piping designer who is familiar with the project.

How do we do the Preliminary Piping MTO?

  • Identify the number of lines and the line classes.
  • Identify the potential routing of each line shown on the P&ID and identify a routing for this line on the plot plan.
  • On a preformatted spreadsheet, enter the line number and piping material spec.
  • For each line number – Determine the pipe length, and estimate the number of fittings (This should be broke down into Elbows, Tees, reducers, flanges, etc.) and group them by size.
  • Valve counts may be taken directly from the P&IDs.
  • HP Vents & LP Drains would be SWAG (Scientific wild Ass Guess)!
  •  Now, move on to the next line, and repeat.
  • Yellow off each line on the P&ID as you go.
  • Once all the lines are yellowed off, they can be checked, and the data collated into the Preliminary Piping Bill of Materials document.  

Secondary MTO:

There are 2 reasons for doing a Secondary piping MTO.

  • To update piping quantities, so that purchase orders for piping materials can be issued.
  • To update the project estimate.

The Secondary piping MTO is done when there is significant progress on the piping design, whether done in 3D or 2D.

That said, it must be done early enough to ensure that the procurement of the piping materials will fit the overall project schedule.
This is a joint effort between the piping designers and the Material Control Group.

How do we do the Secondary Piping MTO?

When using intelligent, spec driven 3D models, the Material Control Group would access (or be given) the electronic data base and down-load all the material available at that time.
The Piping Design Leads need to allow for work not yet complete, and convey this information to the material control group, so that this can be factored into the estimate.

If you are using a manual / 2D design method, this is a more labour intensive exercise, and all the components, Pipe, Elbows, Tees, reducers, valves, flanges, gaskets, bolts, etc. must be counted, line by line, checked, the data collated, and then passed along to the material control group, along with the allowance for work not yet complete. 

Final Piping MTO:

The final piping MTO will identify any late additions to the project, and should serve to catch anything that may have been missed in earlier piping MTOs.

The Final Piping MTO will also nail down the final job costs.

The Final Piping MTO is produced when the last Isometric has been drawn, checked, approved and issued.

Again, this is a joint effort between the piping designers and the Material Control Group. It proceeds in much the same manner as the secondary Piping MTO. Any discrepancies between the Secondary Piping MTO, and the Final Piping MTO would be identified at this stage. Purchase Orders (PO’s) can now be issued with the updated information.  

MTO, “Bump” Philosophy (Piping Material)

Question: Are there any rules that define a minimum percentage of quantity to consider as spare? Could this be divided as per pipes, fittings, diameters and materials also?

Answer: This is a very good question and one that does (or should) come up on every project.
Some companies might refer to this as the "Bump" quantities.

The "Bump" quantity philosophy is an item that may be discussed with the Client early in the project and made it a part of the overall procurement planning.
Remember it not only effects Piping Material but most other bulk materials also.

Things that you and the Client need to consider include:

  • Job Site location
  • Item source location(s)
  • Material Type (common vs. high cost alloy)
  • Are these Construction spares or Operational Spares?
  • Frequency of use or consumption (Example: Gaskets)
  • Logistics & Time for replacement
  • Actual quantity required vs. spare
  • Logic of spares for each item
  • Type of warehouse Space (Secure vs. open storage)
  • Cost of warehouse space
  • Method & Cost of inventory control  

Some companies may use different methods, but this is a basic look at how it should work.
Use it as a guide but please do not be misled that this is the only way an MTO can be done.
I would be very interested to hear your take on how things are done where you are, login and use the comments feature below, to discuss.

Special thanks to James O Pennock (JOP), for his suggestions, help & editorial input.

About the Author


{cb:Anton Dooley is a Piper with 30 years experience covering process plant engineering, design & training. He is the founder of}

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