Woodworking Design: Estimating Lumber

A Material List (Cut List) Tells You the Material You Need; This is How to Buy It

Photo of Kelly R. Smith   by Kelly R. Smith

A woodworking project plan for a table
A woodworking project plan for a table
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So you’ve conceptualized your next woodworking project and it’s time to plan. Most woodworkers go one of two ways, depending on the situation:

  • You are working from a cut list from a plan that you acquired from a woodworking project book or magazine.
  • You are making a custom project and it makes more sense to ferret out your dimensions as you go along. This was the case with my recessed medicine cabinet project. Since every home and bathroom is framed differently, it was insightful to go long on the instructive photos and short on actual dimensions when posting the plans.

Understanding Lumber Grades

Are you a frugal and common sense woodworker? I hope so; the money you can save on one part of your project (usually the unseen parts) can be used to great effect of the decorative parts. That being said, I abhor particle board in furniture construction. Chinese knock-off furniture, we ain’t.

Knowing lumber grades, and shopping accordingly, will stretch your budget and ensure that you work with the appropriate materials. The lumber grades are defined by the National Hardwood Lumber Association, and have been for over 100 years.

Step one, of course, is choosing the appropriate grade. Step two is checking for bark pockets, splitting, checking, bug damage, warping, and more. Take the time to pick through the stock. Don’t take the mis-step of ordering online, going to your Home Depot or Lowes and just let them load it up for you. COVID-19 pandemic or not, this is a hands-on job.

Understanding Lumber Dimensions

Dimension lumber (2 x 4s, 4 x 4s, etc.) is usually softwood stock. Hardwood lumber is at times milled to dimensional sizes, however it is more commonly encountered in random widths and lengths. It is marketed as roughsawn lumber and in variable surfacing options accompanied by these letter and number codes:

  • S2S: Surfaced on two sides.
  • S3S: Surfaced on two sides with one straight-line ripped.
  • S4S: Surfaced on four sides, meaning that the two wide faces are planed and the two edges have been straight-line ripped.
Lumber thickness guide
Lumber thickness guide

Rough lumber is sold in multiples of 1/4″ thicknesses. This means that 4/4 lumber (read as four-quarter lumber) is one inch thick. You will also encounter 5/4, 6/4, and 8/4 thicknesses. Regardless, with any rough lumber thickness, the rule of thumb is to subtract 1/4″ to determine the “finished” lumber thickness following the surfacing procedure.

Calculating lumber board feet
Calculating lumber board feet

Lumber stock is generally offered by the board foot (BF), which is actually a volume measurement. Think of it this way — one board foot of lumber is 1″ thick, 12″ wide, and 12″ long (essentially 144 square inches of 1″-thick lumber). So a 1″-thick board, 6″ wide and 36″ long would be 1.5 board feet of stock. The formula for determining the BF of a specific piece is: (Thickness x Width x Length)/144; QED. See the formula chart above for examples of calculating BF. Note: 3/4″ surfaced lumber is considered 1″ when calculating board feet because it is originally derived from 4/4 rough-sawn lumber. Confused yet? Don’t be.

Buying Lumber

Calculating just how many board feet of lumber you need for any given project is only your first step. Next, you will need to peruse your material list for pieces that have specific length requirements. As an example, if you have coffee table legs that need to be 14″ long or 90″ long bed rails, you should select stock long enough to make those components. Then an excellent guideline is to add 20 to 30 percent more to your estimate for waste (defects, poor grain pattern, building mistakes, etc.). So if your project requires 10BF, procure 13BF instead. Buying a bit of extra lumber is always a good idea, and experience will prove the truth of it. Keep in mind that at times you will need to resort to your biscuit joiner to save the expense of ordering a special width of lumber.

Following these lumber estimating guidelines for your woodworking projects will save you time, money, and extra trips to the lumber yard or local home improvement store.

Further Reading

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About the Author:

Photo of Kelly R. SmithKelly R. Smith is an Air Force veteran and was a commercial carpenter for 20 years before returning to night school at the University of Houston where he earned a Bachelor’s Degree in Computer Science. After working at NASA for a few years, he went on to develop software for the transportation, financial, and energy-trading industries. He has been writing, in one capacity or another, since he could hold a pencil. As a freelance writer now, he specializes in producing articles and blog content for a variety of clients. His personal blog is at I Can Fix Up My Home Blog where he muses on many different topics.


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