Board Foot Calculator

Enter thickness, width and length, add the number of pieces, and get the total board footage and an optional cost at your price per board foot.

Handles the quarter system — 4/4, 5/4, 8/4 — and converts to cubic metres for metric orders.

How to use the board foot calculator

Why use the Build Tally board foot calculator

What a board foot actually is

A board foot is 144 cubic inches of lumber: one square foot at one inch thick. The formula is thickness × width × length in inches, divided by 144, or thickness in inches × width in inches × length in feet divided by 12. It is a volume, not an area, which is the point most people miss — a 1 × 12 board eight feet long and a 2 × 6 board eight feet long are both eight board feet, despite looking nothing alike.

The quarter system and rough versus surfaced

Hardwood thickness is quoted in quarters of an inch: 4/4 is one inch, 5/4 is an inch and a quarter, 8/4 is two inches. That refers to rough thickness before surfacing, so 4/4 lumber surfaced on two sides finishes at about 13/16 inch — but you pay for the 4/4. Board footage on rough lumber is also normally calculated on the rough dimensions, so it is worth confirming with the mill which basis a quote uses, because the difference on a large order is real.

Buying by the board foot

Hardwood is priced per board foot and sold in random widths and lengths, which is very different from buying dimensional softwood. You are buying volume, not specific pieces, so you need extra for cutting to the sizes your project actually requires — 20–30% over the net footage is a common allowance for furniture work, more if you need wide clear boards or matched grain. Take the widths as they come and plan cuts around defects rather than assuming every board yields cleanly.

Read the guide: Deck Materials List: Working Out Boards, Joists, Posts and Fasteners