◧MeasureThenConstruction Calculators

Lumber Calculator

Estimate lumber quantities and board feet for a project.

Mason ReidFounder and Lead Estimator at MeasureThen

Last updated 2026-08-21

What Is a Lumber Calculator?

A lumber calculator estimates how many boards you need for a flat surface such as decking, flooring, or shelving, given the area and the spacing between boards. It also reports the total board feet so you can budget for the wood. It is built for homeowners planning a straightforward board layout across a measured space.

How It Works

Boards = ceil((Width × 12) ÷ Spacing). Board feet per board = (Nominal T × W × Length) ÷ 12.

Example

For a 12 ft × 8 ft area with 16 in spacing and 2×6 boards: 6 boards, 12 bf each, 72 bf total.

How to Calculate

  1. Measure the length and width of the area in feet. For a 12 by 8 foot deck, the area is 96 square feet.
  2. Choose a board size and the spacing between boards. Common decking uses 2x6 boards with a small gap.
  3. Figure out how many boards span the width by multiplying the width in feet by 12 and dividing by the spacing in inches. For 8 feet at 16 inch spacing, that is 96 divided by 16 equals 6 boards.
  4. Multiply the board count by the length to get total linear feet. Six boards at 12 feet long is 72 linear feet.
  5. Convert to board feet by multiplying the linear feet by the board feet per foot for your chosen size, then add a waste factor of 5 to 10 percent.

Decking Board Count by Width and Spacing

Board SizeSpacingBoard Feet per 12 ft Piece
2x416 in8
2x612 in12
2x616 in12
2x816 in16
5/4 x 616 in10
2x624 in12

Sources

Frequently Asked Questions

What layout does this assume?

Boards run the length of the space and are spaced across the width, like decking or flooring.

What lumber size should I pick?

2×6 or 2×8 are common for decking. The size sets the board-feet estimate.

Does this include framing lumber?

No — this estimates the surface boards only, not joists, beams, or fasteners.

Estimate the cost with the Lumber Cost Calculator or browse Lumber Calculators

More Lumber Calculators

Board Feet CalculatorFind the board footage of lumber by entering thickness, width, and length. Add a price per board foot to estimate cost for your project.2x4 CalculatorCalculate the number of 2x4s needed for framing.Framing CalculatorCalculate the exact number of wall studs, plates, and framing lumber. Set stud spacing for 16 in or 24 in on center and account for openings.Stud CalculatorCalculate the number of wall studs needed.Lumber Cost CalculatorEstimate the total cost of lumber from board feet and price per board foot. Adjust for species, waste, and quantity to budget your project.

Mason ReidFounder and Lead Estimator at MeasureThen

Mason Reid founded MeasureThen after two decades of hands-on work in construction and estimating. Across residential and light commercial projects, he sized concrete pours, framed walls, hung drywall, and priced out roofing, fencing, and deck work — learning the exact math that every job depends on. At MeasureThen he writes the formulas, checks every calculator against real-world assumptions, and makes sure each one is simple enough for a homeowner to trust and a contractor to use. When he is not measuring twice, he is helping projects stay on budget.

Every MeasureThen calculator uses simple, transparent formulas and standard industry assumptions drawn from common construction practice. We show the math behind each result and include worked examples so you can follow along and double-check the numbers. Results are estimates: materials, labor, and pricing vary by region and market, so always confirm important figures with a licensed professional and your local building codes.