Lumber Calculator
Calculate lumber needs for your construction project including board feet, linear feet, and number of boards from standard lengths. Also see our Board Foot Calculator, Deck Calculator, and Framing Calculator.
How to Use the Lumber Calculator
Select your project type (deck, fence, or framing) to help determine appropriate waste factors. Choose your board dimensions from standard lumber sizes. Enter the length needed per piece and how many pieces you require. The calculator computes total board feet, total linear feet, and tells you how many standard-length boards to purchase from your lumber supplier. Adjust the waste factor based on project complexity — simple straight cuts need less waste allowance than complex angles or curved designs.
For deck projects, typical waste is 10-15% due to end cuts and board-end trimming. Fence projects usually require 5-10% waste for straight picket cuts. Framing projects with headers, cripples, and angled cuts may need 15-20% waste allowance. The calculator shows results for all standard lumber lengths (8, 10, 12, and 16 feet) so you can choose the most economical option from your local supplier.
Lumber Buying Tips
When purchasing lumber, inspect each board for straightness, checking for bow, twist, cup, and crook. Sight down the edge of the board to identify warping. Avoid boards with large knots near edges, excessive wane (bark edge), or splits at the ends. Pressure-treated lumber should be stacked flat with spacers (stickers) between layers to allow air circulation and prevent warping during acclimation.
Formula
Board Feet = (Thickness x Width x Length) / 12
Total Linear Feet = Length per piece x Quantity
Boards from standard length = Total LF / Standard length (rounded up)
Waste = Total BF x (Waste% / 100)
Example Calculation
Project: 20 pieces of 2x6, each 8 ft long, 10% waste
Total Linear Feet = 8 x 20 = 160 LF
Board Feet = (2 x 6 x 160) / 12 = 160 BF
Waste = 160 x 0.10 = 16 BF
Total with waste = 176 BF
Boards from 8 ft stock = 160 / 8 = 20 boards
Boards from 12 ft stock = 160 / 12 = 14 boards
Reference Table: Nominal vs Actual Lumber Dimensions
| Nominal Size | Actual Size (in) | BF per 8 ft | BF per 12 ft | BF per 16 ft |
|---|---|---|---|---|
| 2x4 | 1.5 x 3.5 | 5.33 | 8.00 | 10.67 |
| 2x6 | 1.5 x 5.5 | 8.00 | 12.00 | 16.00 |
| 2x8 | 1.5 x 7.25 | 10.67 | 16.00 | 21.33 |
| 2x10 | 1.5 x 9.25 | 13.33 | 20.00 | 26.67 |
| 2x12 | 1.5 x 11.25 | 16.00 | 24.00 | 32.00 |
| 4x4 | 3.5 x 3.5 | 10.67 | 16.00 | 21.33 |
Frequently Asked Questions
How much lumber do I need for a 12x16 deck?
A standard 12x16 ft deck using 2x6 decking at 16' OC joist spacing requires approximately 35 decking boards (12 ft long), 13 joists (2x8 or 2x10 at 12 ft), and 2-3 beams. Total lumber is roughly 350-400 board feet including framing and decking.
What waste factor should I use for lumber?
Use 10% waste for simple straight-cut projects like fencing. Use 15% for standard framing with some angles. Use 20-25% for complex projects with many cuts, angles, or curved work. If working with lower-grade lumber that may have defects, add an additional 5-10%.
What is the difference between board feet and linear feet?
Linear feet measures only the length of lumber, regardless of width or thickness. Board feet measures volume: (thickness x width x length) / 12. A 2x6 at 10 feet is 10 linear feet but 10 board feet. A 2x12 at 10 feet is still 10 linear feet but 20 board feet.
Which standard lumber length should I buy?
Buy the shortest standard length that accommodates your cuts to minimize waste. Standard lengths are 8, 10, 12, 14, and 16 feet. If you need 7 ft pieces, buy 8 ft boards. If you need 9 ft pieces, buy 10 ft boards. For multiple shorter cuts, calculate how many fit per board.
Is pressure-treated lumber sized differently?
No, pressure-treated lumber uses the same nominal and actual dimensions as untreated lumber. A pressure-treated 2x6 is still 1.5 x 5.5 inches actual. However, PT lumber may be slightly heavier due to the chemical treatment and higher moisture content.
How do I calculate lumber for a fence?
For a standard 6 ft privacy fence: posts (4x4) every 8 feet, 2 or 3 horizontal rails (2x4) per section, and pickets (1x6 or 1x4) to cover each section. For a 100 ft fence with 8 ft spacing, you need 14 posts, 28-42 rails, and approximately 200 pickets (1x6 with small gaps).