How to Calculate Lumber for Projects?

This question comes from Zach who asks:

Hey Marc, I’m a new woodworker and I’m having trouble trying to figure out how much lumber I need for each project. I know how to calculate the amount of board feet needed, but that doesn’t factor in how much material is lost from saw blades and the countless errors I’m bound to make. So, I guess what I’m trying to ask is do you have any sort of formula for calculating the amount of material needed for a project?

And this was my response:

Basically there are two ways I approach this. The “lazy” way and the “accurate” way. The lazy way is to take that board foot number and add about 15-20% to it. Then go to the lumber supplier and buy that many board feet. Now the drawback to this is the fact that you might wind up with the wrong set of boards. For instance, if your project calls for a bunch of long pieces, you might have the right total number of board feet but the boards might not be long enough. So you may wind up making another trip to the lumber supplier if you use this method.

Now the accurate method is to plan everything out on paper. Lets assume you have access to rough boards that are 8′ long and 6-7″ wide. I would draw a bunch of “blanks” on a piece of paper and then try to plan out the cuts for all of your project parts. Keep in mind things like milling and kerf widths since the goal is to be as realistic as possible. You may have to erase a few boards and reorganize them for the sake of saving wood, but eventually you should have a nice cut diagram. The interesting part of this process is that you don’t really need to be concerned with board feet. Instead you want to make sure you are getting the right number of boards so you can make cuts according to your diagram. This process takes a while but it can be worth it since the “lazy” way can be frustrating and disappointing. And furthermore, it makes it much easier to select that perfect wood grain while you are at the lumber yard. Don’t be a afraid to bring a piece of chalk with you so you can mark the boards up as you place them in your cart or vehicle.

Most times, I do a bit of both techniques. If I have a bunch of smaller parts, I lump them into a board foot number and make sure I have that number plus 15%. For larger pieces, I make sure I have the right number of boards. And for certain parts of projects, you want to take it one step further by picking very specific boards. For instance, a table top. You don’t want to let fate decide which boards make a bold statement in your project. So ultimately, a combination of those two techniques is what works for me. Hope this helps.

Category: Techniques

Comments

  1. Michael Morton July 14, 2009

    It was interesting to read in the latest Woodworking Magazine (I think it was Chris Schwarz writing) that he adds on 50% or 100% in order to have plenty of wood to pick through to get the right grain pattern and orientation for the final parts. Yes, a lot more wood and $$ than your standard 15-20%, but his point was that it’s worth it to get the right grain/patterns for a piece you’re going to put a lot of time into. And of course, there’s plenty of ways to use the remaining wood in future projects!

    • Marty July 14, 2009

      Wow, not that I should even think about questioning The Schwarz but that is a LOT of waste. Most lumber yards will let you pick through their stock if you put back what you don’t buy. Hence, I like Marc’s suggestions.

  2. Skee July 14, 2009

    The thing I’ll say about the lazy method is that it is fast and easy on the mind. The hard part is you might end up gluing up panels of 4″ wide boards to get some 6″ stuff you need at a certain place in the project.

    You can also radically impact the amount of waste for a project by being very picky about grain patterns and “Correct” boards. This is up to the craftsman to decide, in my opinion. Some people want to economize and get as much out of each board as possible. Some people want to build art and want all the grain perfectly straight throughout. As with most things, the best course is a compromise, as Marc suggests. Estimate for the little stuff, worry about the big, flat surfaces.

    Matt, over at Matt’s Basement Workshop always ends each show with “Straight Grains” or something like that, so I figure he must be an artist who wastes 300-400% of his lumber. [I always want to flip his ending around - Straight blades and sharp grains - just sounds fun]

  3. Loupitou06 July 14, 2009

    I also use a blend of lazy/accurate method :
    I draw a very rough sketch in Google Sketchup using components for the idems I care for (top, door panels,…), with this I get an idea of the proportions and a nice sketch to show to my wife for acceptance.
    Then I run the cutlist plug-in with several board width options (4″, 6″ and 8″).
    I end up with 3 precise cutlists with the most common board width.
    Now in the lumber store, if the wood I like for the top is available only in 6″, I’ll use the number or board foot from this cutlist and so and so forth.
    The idea is to optimize the yield of each component, given the availability at the lumberyard.

    Then of course I add some margin 10 to 20% since I do some stupid mistakes and you never know what a board will look like once planned or re-sawn

    With this method, I can get very good yield so far.

    Hope this helps and hats off the developer of the cutlist plugin for Sketchup !

  4. BedrockBob July 14, 2009

    I use CorelDraw to layout all the parts to the project and label the sizes of each part. Then I figure out roughly how may boards I will need using 8รข

  5. Ken_in_kanata July 15, 2009

    I guess I lean more on the lazy side of things. I have an idea especially for the larger pieced on length and width but basically I tend to over (WAY over sometimes) estimate what I need have lots of material to pick from back at the shop. The nice thing about doing it this way is you end up with a stock pile of wood for future projects. When I do need to figure out board feet I use this on line board foot calculator. http://www.westwindhardwood.co.....lator.html

  6. Brock July 17, 2009

    I use Smart Cut Pro, it is an optimization software primarily for panels. I use it for board layouts and it works fine. Also it provides a cut list, labels and loads of other stock management features, a free download to try. I think it limits to 10 parts after 30 days. Really worth looking at.

    http://www.rasterweq.com/specifications.htm

  7. va2bmg July 17, 2009

    If you are a bit on software side, there is one that works pretty good and can account for a few factors and is based on a cutlist, which is the name of the software actually.

    There is different version/feature with diffrent price tags depending on what you need. This will give you how much board of sheet for a project, but will not account for specifics in the wood when at the lumberyard, i.e. figure in wood for a particular piece(s) that you’d like or variying dimentions available.

    The web site is http://www.cutlistplus.com. Again, it ain’t perfect but can save some trouble and is one way to serve up as a good estimate on how much you need.

  8. Tom June 15, 2011

    You could also use sketch-up as part of your planning for the important parts to figure out how many boards you will need

  9. josh March 18, 2013

    Hey Marc, you mentioned how the lazy way might result in the correct number of board feet but not the right boards to yield the lengths you need. How do you avoid this when ordering online? That’s my biggest confusion with board feet right now, making sure I get the right boards and not just the right board feet.
    Thanks for all the great information and help for us noobs!

    •  

      Well the only way to avoid it is to order a lot more or to simply plan better. Also make sure you know exactly what they are sending, in terms of general board length and width. If you plan it out board for board, you can get pretty close. But keep in mind the big disadvantage of mailorder: you don’t know what the grain looks like. So ordering extra is always a good idea.

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