How to measure for your deck board project
- Measure your deck area. Walk the deck with a tape and measure length × width in feet. For an L-shaped or wraparound deck, break it into rectangles, calculate each section separately, and add the areas together. Enter the total square footage in the Deck area field.
- Enter board width and length. Standard 2×6 and most composite boards are 5½ inches wide — the calculator's default. If you're using 5¼-inch composite grooved boards, enter 5.25. Choose the longest board length that fits your deck dimension with little cutting waste (16 ft is the most common stocked length).
- Set a waste allowance and read the result. Leave the waste at 10% for a straight layout. Bump it to 15% for a diagonal pattern. The calculator returns the total number of full-length boards to buy and the linear footage — useful when ordering by the linear foot from a supplier.
How the deck board calculator works
The calculator converts deck area into linear feet of decking, then divides by board length. First it turns board width from inches to feet (5.5 ÷ 12 = 0.4583 ft), then divides deck area by that coverage width to get the net linear feet needed. It multiplies by (1 + waste/100) to add the waste factor, then divides by board length and rounds up to the next whole board. For a 200 sq ft deck with 5½-inch boards at 16 ft and 10% waste: 200 ÷ 0.4583 = 436 linear feet × 1.10 = 480 linear feet, and 480 ÷ 16 = 30 boards.
Which type are you estimating?
Pressure-treated lumber (straight layout)
The most affordable option. Standard PT 2×6 boards are 5½ inches wide and come in 8, 12, 16, and 20 ft lengths. A straight, parallel-to-the-house layout gives the least cut waste and the lowest board count.
Enter: Board width: 5.5 in · Board length: 16 ft · Waste: 10%
Cedar or redwood (straight layout)
Same dimensions as PT — 2×6 boards are 5½ inches wide. Cedar and redwood are lighter and naturally rot-resistant. Run the same numbers as pressure-treated; the board count is identical for identical dimensions.
Enter: Board width: 5.5 in · Board length: 16 ft · Waste: 10%
Composite or PVC (grooved, hidden fasteners)
Most composite decking is ¾-inch narrower at 5¼ inches (actual 5.25 in) to leave room for hidden clip fasteners. Switching from 5.5 to 5.25 adds a few boards — a 200 sq ft deck needs 32 boards instead of 30 at the same waste.
Enter: Board width: 5.25 in · Board length: 16 ft · Waste: 10%
Diagonal pattern
Running boards at 45° to the joists looks striking but creates more off-cuts at every rim joist, adding roughly 15% extra waste. Raise the waste allowance to 15% (or even 20% on small decks with many corners) to cover the added cut loss.
Enter: Board width: 5.5 in · Board length: 16 ft · Waste: 15%
Picture-frame or border boards
A picture-frame border runs boards perpendicular to the field boards around the deck perimeter. Calculate the field area and border area separately, add the totals, and use 10% waste for each section. A 16×16 deck with a two-board border adds roughly 4–6 extra boards on top of the 39 the calculator returns for the full area.
Enter: Calculate field + border areas separately · Waste: 10% each
Tips & ways to save
- Pick a board length that divides your deck span cleanly — a 12-ft-wide deck covered with 12-ft boards has zero end-cut waste, while 16-ft boards leave a 4-ft off-cut on every run.
- Add 15% waste (not 10%) for diagonal patterns; the angled end cuts at both rim joists waste roughly one extra board in every seven.
- Always order at least one or two extra boards beyond the calculator's count — you'll want spares on hand for knots, splits, or future repairs years from now.
- Linear footage is the number to give your lumber yard or composite supplier when ordering by the piece from a cut-list; the board count is what you need when buying full-length sticks off the rack.
- For an L-shaped deck, measure each rectangular section separately (length × width), add the areas together, and enter the combined total — the calculator handles any square footage you give it.
Deck boards by deck size (5½-in boards, 16 ft long, 10% waste)
| Deck size | Deck area | Linear feet | 16-ft boards |
|---|---|---|---|
| 10 × 10 ft | 100 sq ft | 240 ft | 15 |
| 12 × 12 ft | 144 sq ft | 346 ft | 22 |
| 12 × 16 ft | 192 sq ft | 461 ft | 29 |
| 16 × 16 ft | 256 sq ft | 614 ft | 39 |
| 16 × 20 ft | 320 sq ft | 768 ft | 48 |
For 5½-inch-wide boards (standard 2×6 or composite) at 16 ft long with 10% waste. Narrower 5¼-inch boards need a few more. Diagonal or picture-frame layouts add waste.
Frequently asked questions
How many deck boards do I need for a 12×16 deck?
How many deck screws do I need?
How many screws go in each deck board?
How much extra decking should I order for a diagonal pattern?
What is the difference between 5.5-inch and 5.25-inch deck boards?
How do I calculate deck boards for an L-shaped deck?
Sources
Related calculators
Reviewed by the BackyardCalc editorial team. Figures are computed from the formula above and checked against manufacturer yields.