Board Foot Calculator

By Uzair Arshad , Senior Civil and Structural Engineer

Last updated: April 27, 2026

This board foot calculator converts board dimensions into board feet so you can estimate lumber volume, waste, and cost before placing an order. Enter thickness, width, length, and quantity to get per-board and total board feet with optional pricing.

How to use this calculator

Enter the board thickness in inches. Use decimals for quarter sizes: 0.75 for 3/4 lumber, 1.25 for 5/4 lumber, 2.0 for 8/4. Measure the actual thickness, not the nominal label, when precision matters.
Enter the board width in inches. Measure across the face of the board. For rough-sawn hardwood, use the actual measured width from your supplier rather than relying on a rounded label.
Enter the board length in feet. Common lumber lengths include 8, 10, 12, and 16 feet. Use decimals for boards that fall between even-foot lengths (8.5 ft for an 8 ft 6 in board).
Set the quantity. Enter the number of boards with the same dimensions. If you have boards of different sizes, run this board foot calculator once for each size and add the totals.
Add price per board foot (optional). Type your supplier's price to get a cost estimate before tax or delivery fees. Leave it at zero if you only need the board footage total.
Choose a waste allowance. Select 10% for general construction and woodworking. Pick 15% or 20% for furniture builds, live edge slabs, or projects where you need to match grain and color across multiple boards.

Pro tip: I learned this the hard way on a walnut bookshelf project. Buying the exact calculated board footage left me one plank short after trimming end checks and rejecting a warped board. Add at least 10% waste to avoid a second trip to the lumber yard, especially when your supplier charges a delivery fee per load.

Multiple board sizes: If your project uses different dimensions (for example, 8/4 walnut for legs and 4/4 walnut for panels), run this board foot calculator once per size and add the totals. Keep a running tally so you can give the supplier one combined order.

How the calculation works

Board feet:
Board feet per board = Thickness (in) × Width (in) × Length (ft) / 12

Totals:
Total board feet = Board feet per board × Quantity
Waste-adjusted BF = Total board feet × (1 + Waste % / 100)

Cost:
Estimated cost = Waste-adjusted BF × Price per board foot

Thickness: Board thickness in inches (use actual measured thickness for accuracy)
Width: Board width in inches, measured across the face
Length: Board length in feet
Quantity: Number of boards with the same dimensions
Waste %: Extra material for cuts, defects, and selection losses (default 10%)
Price per BF: Supplier's price per board foot for cost estimation (optional)

A board foot is the standard unit for measuring and pricing sawn lumber. One board foot equals a piece of wood 12 inches long, 12 inches wide, and 1 inch thick, or 144 cubic inches of material. Hardwood dealers, sawmills, and specialty suppliers price stock by the board foot rather than by the piece.

Main formula:

Board feet = Thickness (in) × Width (in) × Length (ft) / 12

Variables:

Thickness = board thickness in inches. Common rough values: 1.0 (4/4), 1.25 (5/4), 1.5 (6/4), 2.0 (8/4).
Width = board width in inches, measured across the face.
Length = board length in feet.
12 = the divisor that converts the mixed-unit product (in × in × ft) into board feet.

Thickness and width use inches because that's how lumber is labeled at the yard. Length uses feet because boards are sold in foot increments. The formula divides by 12 to normalize these mixed units into one board foot.

Example:

5 boards, each 1.25 in thick, 10 in wide, and 8 ft long, with 10% waste at $4.15 per board foot.

Step	Calculation
Board feet per board	1.25 × 10 × 8 / 12 = 8.33 BF
Total board feet	8.33 × 5 = 41.67 BF
Waste (10%)	41.67 × 0.10 = 4.17 BF
Waste-adjusted total	41.67 + 4.17 = 45.83 BF
Estimated cost	45.83 × $4.15 = $190.21

Nominal vs. actual dimensions:

Nominal lumber sizes (2x4, 2x6, 1x6) don't match actual dimensions. A nominal 2x4 measures 1.5 × 3.5 inches after planing. If you enter nominal sizes into this board foot calculator, the result will overstate the real volume. Rough-sawn hardwood is typically sold at actual thickness (4/4 = ~1 in, 5/4 = ~1.25 in, 8/4 = ~2 in), so use the thickness your supplier quotes.

Common mistake:

Entering length in inches instead of feet creates a result 12 times too high. Always enter length in feet. For boards between even-foot lengths, use a decimal: 8 feet 6 inches = 8.5 ft.

Waste factor:

Waste covers material lost to crosscuts, end checks, knots, warped boards, and grain selection. A 10% waste factor works for most construction and general woodworking. Raise it to 15% or 20% for furniture builds or when selecting for color and figure. Buying the exact calculated board footage often leaves you short after trimming defects.

Quick rule:

A 1 in thick board that is 12 in wide and 1 ft long = exactly 1 board foot
Hardwood typically runs $4 to $15 per board foot depending on species (2026 prices)
1,000 board feet = 1 MBF, the unit mills and dealers use for bulk pricing
A log board foot calculator uses Doyle, Scribner, or International log rules and is a different tool

Board feet vs. square feet and linear feet:

Unit	Measures	Conversion to board feet
Board feet	Volume (thickness × width × length)	Base unit
Square feet	Area (width × length, ignores thickness)	BF = sq ft × thickness (in) / 12
Linear feet	Length only	BF = lin ft × thickness (in) × width (in) / 144

These conversions only apply to uniform rectangular lumber with consistent dimensions.

Assumptions and limitations:

This board foot calculator assumes rectangular sawn lumber with uniform dimensions. Live-edge slabs, tapered stock, or irregular shapes need manual measurement at the widest and narrowest points, then averaged.
The calculator does not account for surfacing loss. Rough lumber planed to finished thickness yields slightly less usable volume than the raw board foot total.
Cost estimates use a flat rate per board foot. Suppliers may price differently by species, grade, or quantity tier.
Log scaling (Doyle, Scribner, International) is a separate measurement system. Don't use this calculator for logs, spray foam, drywall, or other materials measured differently.

Frequently Asked Questions

How to calculate board foot

Multiply thickness in inches by width in inches by length in feet, then divide by 12. For example, a board that is 1 inch thick, 10 inches wide, and 8 feet long equals 6.67 board feet. Multiply by quantity for a project total.

How is board foot calculated

Board foot measures lumber volume, not surface area. One board foot equals 144 cubic inches, or a piece that is 1 inch thick, 12 inches wide, and 12 inches long. A 2 inch by 6 inch by 8 foot board equals 8 board feet when using nominal dimensions.

How do you calculate a board foot of lumber

Measure lumber thickness and width in inches, then measure length in feet. Multiply those three values and divide by 12. For 5 boards that are 1.25 inches thick, 10 inches wide, and 8 feet long, the total is 41.67 board feet.

How to calculate board foot price

Multiply total board feet by price per board foot. If your project needs 41.67 board feet and the lumber costs $4.15 per board foot, the estimate is $172.93 before tax, delivery, and waste. Add 5% to 10% extra for cuts and defects.

What is a board foot calculator

A board foot calculator estimates lumber volume from thickness, width, length, and quantity. It helps when hardwood, slabs, or rough lumber are sold by board foot instead of by piece. For example, compare 5/4 × 10 walnut boards against 4/4 × 8 cherry to see which order totals fewer board feet.