Board Foot Calculator

Enter the thickness, width and length of each board. You get board feet, cost and cubic meters as you type. Add more boards to build a full cut list.

What is a board foot?

A board foot is a unit of wood volume. It equals a piece 1 inch thick, 12 inches wide and 12 inches long, which is 144 cubic inches. Any piece that holds 144 cubic inches of wood is one board foot. Hardwood lumber in the United States is bought and sold by this unit.

Penn State Extension and Ohio State University Extension both define the board foot this way [1] [2]. The short forms are bd ft, BF and FBM.

How do you calculate board feet?

Multiply the thickness in inches by the width in inches by the length in feet. Then divide by 12. If all three sizes are in inches, divide by 144 instead. Multiply by the number of pieces for the total. A board 1 inch thick, 6 inches wide and 10 feet long holds 5 board feet.

Board feet = thickness (in) × width (in) × length (ft) ÷ 12
Board feet = thickness (in) × width (in) × length (in) ÷ 144

This is the formula given by the University of Wisconsin Extension and the American Hardwood Export Council [3] [4]. See our step by step guide for more worked examples.

What do 4/4, 5/4 and 8/4 mean?

Hardwood thickness is named in quarters of an inch. 4/4 (four quarter) is 1 inch, 5/4 is 1 1/4 inches, 6/4 is 1 1/2 inches and 8/4 is 2 inches. These are rough sawn sizes. Board feet for hardwood are figured on this nominal thickness, even when the board is sold planed.

The quarter system and the rule that the tally uses nominal thickness come from the National Hardwood Lumber Association grading rules, as summed up by AHEC and the University of Washington [4] [5]. Pick the quarter size from the thickness menu, or choose Other to type any thickness.

Should I use nominal or actual size?

Use the size your seller uses for the tally. Lumber is almost always sold on nominal size. A 2x6 that is 10 feet long counts as 10 board feet. Its planed size of 1 1/2 by 5 1/2 inches holds only 6.875 board feet. Use actual sizes when you need the true volume of wood.

The 2x6 example comes from the University of Wisconsin Extension [3]. Planed hardwood is thinner than its quarter name. The table below shows the standard surfaced two sides (S2S) thickness for common sizes, from the hardwood thickness table in Chapter 6 of the Wood Handbook [6].

How do I find board feet in a live edge slab?

Measure the thickness and the length. Then measure the width at several points and take the average, since slab edges are not straight. Enter those three numbers as one board. A slab 2 inches thick, 20 inches wide on average and 72 inches long holds 20 board feet.

For tapered hardwood boards, the grading rules measure width at one third of the length from the narrow end [5]. Some slab sellers use their own method, so ask how they measure before you compare prices.

How much waste should I add?

There is no single right number. Waste depends on the grade you buy, defects like knots and checks, and how many short or narrow parts your plan needs. Rough lumber also loses thickness and width when you plane and joint it. Enter a percent that matches your past jobs. The calculator adds it to the total board feet and to the cost.

How do I convert board feet to cubic meters?

One board foot is 144 cubic inches. One inch is exactly 0.0254 meters, so one board foot is 0.002359737216 cubic meters. One cubic meter is about 423.78 board feet. Twelve board feet make one cubic foot. The calculator shows both values under the total.

The inch to meter factor is from NIST Special Publication 811 [7]. Switch the units to mm and meters if your lumber is sold in metric sizes.

Can I find board feet in a log?

A log is round, so the simple formula does not work. Foresters use log rules such as Doyle, Scribner and International 1/4 inch. Each one gives a different answer for the same log [8]. Use our log board feet calculator to compare all three.

How this calculator works

• Each line uses thickness × width × length ÷ 12, with length in feet. Inches are divided by 12 first.
• Metric lines use thickness (m) × width (m) × length (m) ÷ 0.002359737216.
• The total adds every line times its quantity. Waste is then added as a percent. Cost is total with waste times your price.
• The hardwood tally option counts any board under 1 inch thick as 1 inch.
• Math runs at full precision. Results are shown to two decimals.
• Your inputs stay in your browser. The share link stores them in the page address.

Need prices per piece or per linear foot? Try the lumber cost calculator. Want a printable table? See the board foot chart.

Questions

References

1. Forest Stewardship: Terminology. Penn State Extension.
2. Measuring Standing Trees (F-35-02). Ohio State University Extension.
3. What Is a Board Foot? Forestry Facts No. 42. University of Wisconsin Extension.
4. Grading Sawn Lumber: Measurement. American Hardwood Export Council.
5. Briggs, D. Forest Products Measurements and Conversion Factors, Chapter 4, Lumber. University of Washington, Rural Technology Initiative.
6. Wood Handbook: Wood as an Engineering Material (FPL-GTR-282), Chapter 6, Commercial Lumber. USDA Forest Service, Forest Products Laboratory, 2021.
7. NIST Special Publication 811, Appendix B.9, Conversion Factors. National Institute of Standards and Technology.
8. Cassens, D. Log and Tree Scaling Techniques (FNR-191). Purdue University Extension.

Written and checked by the editors of Board Foot Calculator. Every formula on this page is tested with sample values from the sources above. How we work. Last updated: October 20, 2026.