Board Foot Calculator

Calculate board feet for one or more stacks of lumber from the thickness, width and length, including quarter-sawn hardwood sizes like 4/4 and 8/4, with extra for waste and the cost at a price per board foot. Your inputs stay in your browser.

Your lumber

Your lumber

Thickness in inches or quarters (4/4 = 1 in, 5/4 = 1¼ in, 8/4 = 2 in). Use nominal sizes: a 2×6 is 2 by 6. Rows 2 to 4 are optional.

Stack 1
Stack 2 (optional)
Stack 3 (optional)
Stack 4 (optional)

For defects and offcuts; 15% to 30% is common for rough hardwood.

84.33 bd ft including 15% extra (73.33 bd ft net). See full results

Example: 10 boards 4/4 × 6 in × 8 ft and 4 boards 5/4 × 8 in × 10 ft, with 15% extra. Enter your lumber to update.

Your board feet

Board feet to buy
84.33 bd ft
73.33 bd ft plus 15% extra
Volume
6.11 cu ft
120 linear feet of boards

Board feet by stack

StackSizeEachTotal
10 × stack 1 1 in × 6 in × 8 ft4.00 bd ft40.00 bd ft
4 × stack 2 5/4 in × 8 in × 10 ft8.33 bd ft33.33 bd ft
Total 73.33 bd ft

Add a price per board foot to estimate the cost.

Board foot formula

A board foot is a volume of 144 cubic inches: a board 1 inch thick, 12 inches wide and 1 foot long. For a board T inches thick, W inches wide and L feet long:

board feet = T × W × L ÷ 12

If you measure the length in inches, use T × W × L ÷ 144 instead (NIST: tables of units of measurement).

  • A 4/4 board 6 inches wide and 8 feet long: 1 × 6 × 8 ÷ 12 = 4 board feet, so 10 of them are 40.
  • A 5/4 board 8 inches wide and 10 feet long: 1.25 × 8 × 10 ÷ 12 = 8.33 board feet.
  • A 2×6 that is 8 feet long: 2 × 6 × 8 ÷ 12 = 8 board feet.

Quarter sizes and nominal thickness

Hardwood thickness is sold in quarters of an inch, measured rough before planing: 4/4 ("four quarter") is 1 inch and 8/4 is 2 inches. Board feet are figured on this nominal thickness, so surfaced 4/4 lumber planed to about ¾ inch is still priced as 1 inch. Softwood dimensional lumber is also figured on nominal sizes: a 2×6 counts as 2 by 6 inches even though it measures about 1½ by 5½.

Quarter sizes in inches

Quarter sizeNominal thickness
4/4 1 in
5/4 1.25 in
6/4 1.5 in
8/4 2 in
10/4 2.5 in
12/4 3 in
16/4 4 in

Waste and cost

Rough lumber has knots, splits and uneven edges, and cutting to length leaves offcuts, so buy extra: around 15% for clean stock and up to 30% or more for lower grades or projects with many small parts. The example needs 73.33 board feet, or 84.33 with 15% extra; at $6.50 a board foot that is $548.17.

Assumptions and limits

  • Board feet use the thickness and width you enter; enter nominal sizes to match how lumber is priced.
  • Lumberyards may round each board to the nearest foot of length or round the total; the result here is not rounded.
  • Some lumber, such as trim and dimensional softwood at big-box stores, is priced per piece or per linear foot instead of per board foot.

Methodology and testing

Automated tests check the definition (1 × 12 in × 1 ft = 1 board foot = 144 cubic inches), nominal and quarter sizes, several stacks with waste and price, and invalid inputs against hand-worked values. How we build and test calculators.

Sources

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