How Much Lumber Do I Need?
The right lumber quantity for a project depends on the size and type of project, the lumber dimensions, and how much waste to expect. This guide walks through the calculation method and gives reference quantities for common projects.
The General Method
Three steps cover nearly every project:
- Calculate net volume. Find the board feet (or linear feet) your project requires based on dimensions alone — no waste yet.
- Add a waste allowance. Add 10–25% depending on cut complexity and project type.
- Round up to available lengths. Lumber comes in standard lengths (8, 10, 12, 14, 16 ft). Adjust quantities to match what's actually sold.
Use the Lumber Calculator to automate this — enter multiple board sizes with quantities, set a waste percentage, and get a complete summary.
Waste Allowance Reference
| Project type | Waste allowance | Reason |
|---|---|---|
| Simple rectangular deck, shelving, or tabletop | 10% | Straight cuts only; minimal end waste |
| Flooring (strip or plank) | 10–15% | Stagger pattern wastes some ends |
| Framing (walls, joists, rafters) | 10–15% | Cut-to-fit pieces create offcuts |
| Diagonal or herringbone patterns | 15–20% | Angled cuts increase end waste significantly |
| Complex furniture with many short pieces | 15–25% | Short rips and cross-cuts from long boards |
| Stair stringers and curved work | 25–30% | Complex cuts and notching waste a lot |
| High-cost hardwood (figured, large slabs) | 10% | Careful planning minimizes waste; expensive to overbuy |
Common Project Lumber Quantities
Deck Framing and Decking
| Deck size | Decking (5/4×6 boards) | Joist framing (2×8, 16" OC) |
|---|---|---|
| 10 × 10 ft | ~110 BF (incl. 10% waste) | ~180 LF of 2×8 |
| 12 × 16 ft | ~220 BF (incl. 10% waste) | ~320 LF of 2×8 |
| 16 × 20 ft | ~380 BF (incl. 10% waste) | ~480 LF of 2×8 |
| 20 × 24 ft | ~570 BF (incl. 10% waste) | ~640 LF of 2×8 |
Interior Framing (2×4 walls, 8-ft ceiling)
| Wall length | Studs (16" OC) | Plates (bottom + double top) | Total 2×4×8s |
|---|---|---|---|
| 8 ft wall | 7 studs | 3 × 8 ft | ~10 pieces |
| 16 ft wall | 13 studs | 3 × 16 ft (or 6 × 8 ft) | ~19 pieces |
| 24 ft wall | 19 studs | 3 × 24 ft (or 9 × 8 ft) | ~28 pieces |
Shelving (3/4" plywood or 1× solid)
| Shelf config | Approx. board feet needed |
|---|---|
| 4 shelves, 12" deep × 48" wide | 16 BF |
| 5 shelves, 12" deep × 72" wide | 30 BF |
| 6 shelves, 16" deep × 96" wide (bookcase) | 64 BF |
Simple Furniture
| Project | Approx. board feet | Notes |
|---|---|---|
| Workbench top (24" × 72", 1.5" thick) | 18 BF | Glued-up slabs need 20% more for trimming |
| Dining table top (36" × 84", 7/4 thick) | 28 BF | Add 20–25% for milling and glue-up |
| Side table (18" × 24", 4-leg) | 6–8 BF | Legs add significant board footage |
| Adirondack chair (1.25" stock) | 18–22 BF | Many short, narrow pieces |
| Small bookcase (12" × 36" × 72") | 20–25 BF | Includes top, sides, shelves, back cleats |
| Bed frame (queen) | 40–60 BF | Headboard, footboard, side rails, slats |
Converting Square Feet to Board Feet
For flat surfaces like floors, countertops, or panel work, the conversion is:
BF = Square Feet × Thickness (inches)
For 3/4" thick flooring over 200 sq ft: 200 × 0.75 = 150 BF. Add your waste percentage to that.
→ Board Feet to Square Feet Calculator
How to Check Your Math
The fastest way to verify your lumber estimate is to use the Lumber Calculator: enter each board size and quantity as a row, set your waste percentage, and compare the total to your project estimate. Doing this prevents the two most common mistakes: under-ordering (project stalls mid-build) and over-ordering (expensive overbuy of material that may not match the next batch).
Frequently Asked Questions
How much lumber do I need for a deck?
For a 12×16 ft deck floor using 5/4×6 decking boards with 1/8" gaps, you need approximately 200–220 board feet plus 10–15% waste. The exact amount depends on board direction, any cutouts, and local joist spacing.
How much lumber do I need to frame a wall?
A standard 8-foot wall uses approximately one 2×4 per linear foot of wall length (studs at 16" OC) plus a double top plate and single bottom plate. A 10-foot wall section needs roughly 10 studs + 3 plates = 13 pieces of 2×4×8.
What percentage of waste should I add to my lumber order?
Add 10% for simple rectangular projects with straight cuts. Add 15% for projects with diagonal cuts or moderate waste. Add 20–25% for complex angles, curves, short pieces from long boards, or if you are working with higher-cost hardwood.
How do I convert square feet to board feet?
Multiply the square footage by the thickness in inches. A 100 sq ft floor with 3/4" thick boards = 100 × 0.75 = 75 board feet (not counting waste). For 1" thick boards, square feet and board feet are equal.