What is a board foot?

A board foot (bf) is the standard unit of volume for lumber in North America. One board foot equals a piece of wood 1 inch thick, 12 inches wide and 12 inches long — or any combination of dimensions whose product equals 144 cubic inches (e.g. 2″ × 6″ × 12″ = 144 in³ = 1 bf). Lumber yards price hardwoods and rough-sawn softwoods by the board foot, which is why calculating total board footage before you order is essential for budgeting.

What is the board foot formula?

BF = (Thickness in inches × Width in inches × Length in feet) ÷ 12. The division by 12 converts the three dimensions — two in inches and one in feet — into a single unit of volume. You can also write it as (T × W × L) ÷ 144 when all three measurements are in inches.

Should I use actual or nominal dimensions?

Always use actual measured dimensions, not the nominal name printed on the label. A '2×4' is actually 1.5 inches thick and 3.5 inches wide once surfaced (S4S). Using nominal figures will overestimate the board footage — and the cost — by up to 20%. For rough-sawn lumber, measure each board with calipers or a tape measure.

How much waste allowance should I add?

A 10% waste allowance is typical for straight cuts on clear lumber. Budget 15–20% for projects with lots of angled cuts, curved parts or defective boards you need to work around. For figured or highly spalted hardwood where defects are common, 25–30% is not unusual. It is always cheaper to have spare lumber than to make a second trip to the yard.

Does this calculator handle multiple different boards?

Yes. Click '+ Add board' to add as many rows as your project needs. Each row has its own thickness, width, length and quantity, so you can model a complete cut list in one go. The total at the bottom sums every row before applying the waste allowance.

What is the difference between board feet and lineal feet?

Lineal feet (also called linear feet) measure only length — they ignore thickness and width. Dimensional lumber sold at DIY stores (2×4 framing, decking boards) is typically priced by the lineal foot at a standard cross-section. Hardwoods and rough-sawn lumber are priced by the board foot because thickness varies. This calculator works in board feet; for lineal-foot pricing simply enter your board dimensions, note the total length, and price by the foot yourself.

Board Foot Calculator

A woodworking board foot calculator that lets you build a full cut list, add a waste allowance and see an estimated material cost — all in one place. Whether you are pricing a batch of hardwood at the yard or planning an entire furniture project, it replaces the back-of-envelope maths that leads to under-ordering.

How it works

The calculator applies the classic North American board-foot formula to every row in your list:

BF = (Thickness in inches × Width in inches × Length in feet) ÷ 12

The divisor 12 normalises the mixed units: thickness and width are in inches, length is in feet, and one board foot is 144 in³ (1 in × 1 in × 144 in = 1 in × 12 in × 12 in, i.e. 1 ft of a 1″ × 12″ board). The tool multiplies the per-board result by the quantity, sums every row to a net total, then scales by (1 + waste %) to give the gross footage you should order. If you enter a price per board foot, it multiplies the gross figure to produce a cost estimate.

When the metric unit mode is selected the tool first converts millimetres to inches and metres to feet (1 mm = 1/25.4 in, 1 m = 1/0.3048 ft) before applying the same formula, so the result is always in the internationally recognised board-foot unit.

Worked example

Imagine you are building a small bookshelf and your cut list looks like this:

Part	Nominal	Actual dimensions	Qty
Shelves	1×8	0.75″ × 7.25″ × 48″	3
Sides	1×10	0.75″ × 9.25″ × 36″	2
Back panel	1×6	0.75″ × 5.5″ × 48″	2

Converting 48″ and 36″ to feet: 48″ = 4 ft, 36″ = 3 ft.

Shelves: (0.75 × 7.25 × 4) ÷ 12 = 1.813 bf × 3 = 5.44 bf
Sides: (0.75 × 9.25 × 3) ÷ 12 = 1.734 bf × 2 = 3.47 bf
Back panels: (0.75 × 5.5 × 4) ÷ 12 = 1.375 bf × 2 = 2.75 bf

Net total: 11.66 bf. With a 15% waste allowance: 13.41 bf. At a typical hardwood price of $7 per board foot the estimated material cost is around $94.

Nominal vs actual size — the critical detail

Dimensional lumber sold as “2×4” or “1×6” refers to the nominal (rough green) size before drying and planing. The actual dry, surfaced size is always smaller:

Nominal	Actual (surfaced dry)
1×2	¾″ × 1½″
1×4	¾″ × 3½″
1×6	¾″ × 5½″
1×8	¾″ × 7¼″
2×4	1½″ × 3½″
2×6	1½″ × 5½″

Always enter the actual measured dimensions, not the nominal label, for an accurate board-foot count and cost. For rough-sawn hardwood from a sawmill, measure with calipers — thickness can vary significantly along the board.

Formula note

The formula BF = (T × W × L) ÷ 12 with L in feet is exactly equivalent to (T × W × L) ÷ 144 with all three measurements in inches. Both forms appear in woodworking references; this tool uses the mixed-unit convention (inches for cross-section, feet for length) because that matches how North American lumber yards typically quote their stock. Every calculated figure is shown in the Working section so you can cross-check before placing an order.