Lumber Calculator
Estimate full-face board coverage, whole-board quantities, board feet and optional board cost.
This lumber calculator converts your project's length and width, along with your chosen board length, width and thickness, into the number of boards you need and the total board feet to order for a rectangular surface covered edge to edge, without gaps or overlaps. It does not count framing members, wall studs or joists. Enter your dimensions, add a waste percentage for cuts and irregular layouts, and optionally add a price per board to estimate board cost. Separate rows, board direction and reusable offcuts need a cut layout.
For spaced boards use the Deck Board Calculator. For joist counts use the Joist Calculator with your approved layout. Read the lumber estimating guide for measurement and quantity examples.
Switching units converts your dimensions and preserves the same boards and per-board price. Use actual dimensions for physical volume; supplier board-foot billing may use a different basis.
Your Estimate
Project Area
240.0 ft²
Boards Required
66 boards
Total Board Feet
363.0 bd ft
Boards Including Waste
73 boards
Total Board Feet w/ Waste
401.5 bd ft
Full-face area estimate with no gaps or overlaps. Base boards round up first; the selected waste allowance is applied once to that whole-board count, then rounded up again. This is not a cut layout or framing-member count.
Results Actions
Area-based quantities assume full face coverage and do not model board direction, separate rows, offcut reuse, gaps or laps. Verify a cut layout before purchasing. Studs, joists and structural members require a separate layout; board cost excludes labor, tax, delivery and other materials.
Common Lumber Sizes Reference
Sizes shown are actual dressed dimensions. Enter these values into the board width and thickness fields above for accurate board feet calculations.
How to Use the Lumber Calculator
- 1Measure the rectangular surface in feet or meters; switching units converts existing dimensions.
- 2Enter the length, width and thickness of the boards you plan to use (see reference table above).
- 3Choose a project-specific waste allowance. The default 10% is an example, not a universal requirement.
- 4Optionally enter a price per board to see an estimated material cost.
- 5Read your results instantly: boards required, total board feet, and totals including waste.
Example Calculation
For full-face coverage of a 20 ft x 12 ft surface using 8 ft long boards (1.5 in thick, 5.5 in wide) with a 10% waste factor. Project area = 20 × 12 = 240 sq ft. Coverage per board = 8 × (5.5 ÷ 12) = 3.67 sq ft. Using unrounded coverage, round 240 ÷ (8 × 5.5 ÷ 12) up to 66 base boards. Board feet per board = (1.5 × 5.5 × 8) ÷ 12 = 5.5 bd ft, so total board feet = 66 × 5.5 = 363 bd ft. With 10% waste, round 66 × 1.10 up to 73 boards, or about 401.5 bd ft. A cut layout may require a different quantity; this is not a stud count.
Accuracy & Assumptions
- Results are estimates only.
- Coverage assumes full board faces without gaps or overlaps. Board direction, separate rows and offcut reuse are not modeled. Studs and joists require a separate member takeoff.
- The purchase total already includes your selected waste allowance. Choose that allowance for damaged or warped boards; do not add the same waste percentage again.
- Verify all project measurements before purchasing materials.
- Consult a licensed contractor or engineer for structural framing requirements.
Frequently Asked Questions
How many boards do I need to cover a rectangular surface?
Divide your total project area by the coverage of a single board (board length × board width). For a 240 sq ft area covered with 8 ft boards that are 5.5 inches wide, each board covers about 3.67 sq ft, so you would need roughly 66 boards before waste.
What is a board foot?
A board foot is a unit of lumber volume equal to a board 12 inches long, 12 inches wide and 1 inch thick. It is calculated as (thickness in inches × width in inches × length in feet) ÷ 12, and is commonly used when pricing rough or specialty lumber.
How much waste should I add to a lumber order?
Choose waste from your cutting layout, product condition and supplier guidance. The 10% default is an example. This tool applies waste once to the rounded base-board count, then rounds up again.
Can this calculator be used for framing walls?
No. This tool divides surface area by board face area. It does not count spaced studs, plates, headers, blocking or joists. Use a member-by-member takeoff from the approved framing layout.
Does this calculator account for nominal vs. actual lumber dimensions?
No — enter the actual dressed dimensions of your lumber (for example, a nominal 2×6 is actually 1.5 in × 5.5 in) for the most accurate board count and board feet total.
This calculator provides an estimate for planning purposes only. Actual board counts, lumber grades and pricing vary by supplier — always confirm final quantities with your lumber yard before purchasing, and consult a licensed contractor for structural framing.