How to Calculate Board Footage (And Why It Matters When Buying Lumber Online)

If you’ve ever added a board to your cart and wondered why the price jumped when you changed the width or thickness, board footage is the answer. It’s the standard unit hardwood is sold by — and once you understand the formula, pricing lumber for any project takes about ten seconds.

What Is Board Footage?

A board foot is a unit of volume, not length. One board foot equals a board that is 12" long x 12" wide x 1" thick.
It exists because hardwood boards come in random widths and lengths — unlike construction lumber, which is milled to standard sizes. Board footage lets a 6" wide board and a 9" wide board be priced fairly, using the same unit.
This is different from a "linear foot," which only measures length and ignores width or thickness entirely.

The Board Footage Formula

The standard formula is:

Board Feet = (Thickness in inches x Width in inches x Length in inches) / 144

Thickness and width are measured in inches.
Length can be measured in inches (then divide by 144) or in feet (then divide by 12 instead of 144).
The result is your board footage — the number you’ll see multiplied by a per-board-foot price on most lumber sites, including ours.

A Real Example

Let’s say you’re buying a piece of 4/4 (four-quarter) Hard Maple that is 6" wide and 5′ (60") long.

Thickness: 1" (4/4 lumber finishes at roughly 3/4" to 7/8", but is priced at its nominal 1" thickness)
Width: 6"
Length: 60"

Calculation: (1 x 6 x 60) / 144 = 2.5 board feet

If that Hard Maple is priced at $6.00 per board foot, the board would cost $15.00 before any per-board minimums or surfacing fees.

Board Footage vs. Linear Footage

This trips up a lot of first-time buyers:

Linear footage only cares about length — useful for things like moulding or trim, where width and thickness are fixed.
Board footage accounts for length, width, and thickness — which is why it’s the standard for hardwood lumber, where every board can vary in size.
Always check which unit a listing uses before comparing prices between two boards or two sites.

Quick Reference: Common Thicknesses

Hardwood thickness is described in quarters, based on the rough thickness before milling:

4/4 = 1" nominal (finishes around 13/16"–1")
5/4 = 1-1/4" nominal
6/4 = 1-1/2" nominal
8/4 = 2" nominal

Thicker stock uses more board feet for the same width and length, which is why an 8/4 board of the same footprint costs more than a 4/4 board of the same species.

Why This Matters When Buying Online

Knowing the formula means you can estimate cost before you even open a product page — helpful when you’re comparing species or planning a budget.
It helps you buy the right amount. Ordering by board footage (rather than guessing by "a couple of boards") reduces waste and avoids a second order for one extra piece.
Since our S4S boards are surfaced on all four sides and ready to use, the board footage you calculate is footage you can actually build with — no need to account for extra material lost to squaring up rough stock.

Put the Formula to Work

Now that you know the math, browse our S4S lumber and see the board footage pricing in action. Popular starting points include Hard Maple 4/4, Red Oak 4/4, Cherry 4/4, and Hickory 4/4 — all milled smooth on four sides and ready for your next project.