Deck Board Material Calculator

A deck board material calculator returns the number of stock boards to buy. It divides the deck width by one board's width plus its gap to get the rows across. Each row runs the full deck length, so rows times length gives linear feet. Waste is added, then the total is divided by stock length and rounded up.

Last reviewed September 2026Method & sources Report an error

Not to scale.

Stock Boards to Buy

Includes a 10% waste allowance.

Shopping list

Deck boards29 16 ft boards26 rows across the deck width.

Breakdown
Stock Boards to Buy	29
Board Rows Across	26
Total Linear Feet (with waste)	457.6 ft
Estimated Cost

How to Calculate Deck Board Material

Boards run the deck's length, laid side by side across its width, so each board takes up its own width plus the gap next to it. That combined figure (the "pitch") divides into the deck's width to get the number of rows. Each row needs one deck-length's worth of board, so rows × deck length gives the total linear footage of decking needed. A waste allowance covers cut ends and staggered joints. The result is divided by the stock board length (commonly 8-20 ft) and rounded up to a whole board, since boards are sold by the piece, not the linear foot.

Example: 16 ft × 12 ft deck (boards running the 16 ft length)

A 16 ft × 12 ft deck (boards running the 16 ft length), 5.5 in. actual board width, 1/8 in. gap, 16 ft stock boards, 10% waste: 1. Pitch per row: 5.5 + 0.125 = 5.625 in. = 0.469 ft 2. Rows across the 12 ft width: 12 ÷ 0.469 = 25.6, rounded up to 26 rows 3. Raw linear feet: 26 × 16 = 416 ft 4. With 10% waste: 416 × 1.10 = 457.6 ft 5. Stock boards (16 ft each): 457.6 ÷ 16 = 28.6, rounded up to 29 boards 29 sixteen-foot boards cover this deck's 26 rows with enough left over for cuts and staggered end joints.

Deck Board Material: Compare Scenarios

Scenario	Stock Boards to Buy	Board Rows Across	Total Linear Feet (with waste)
Small (10×10 ft deck)	16	22	242 ft
Medium (16×12 ft deck)	29	26	457.6 ft
Large (24×16 ft deck)	58	35	924 ft

What Is Deck Board Material?

A deck board calculator converts a deck's dimensions, board width, and the gap left between boards into how many stock-length boards to buy. The gap between boards isn't just a look. It lets water drain through, and it gives pressure-treated lumber room to expand and contract as its moisture content changes. Leaving it out of the material count would under-order the actual number of rows needed.

Deck Board Material: Pros and Cons

Pros

Accounts for the gap between boards in the row count, not just the board width, which is a common source of under-ordering when the gap is ignored
Supports the common range of stock board lengths, since matching stock length to deck length reduces waste from cutting long boards down
Shows the intermediate row count so you can sanity-check the layout against your actual joist spacing before ordering

Cons

Doesn't size joists, blocking, or fasteners. See the Framing calculator for joist layout, and budget deck screws or hidden fasteners separately
Assumes boards run the full deck length in straight rows. A picture-frame border, diagonal pattern, or multiple deck levels needs each section calculated separately
A single stock length is assumed throughout. Mixing stock lengths to reduce waste on a deck longer than the longest available board needs manual planning

Deck Board Material: What a Pro Checks

Leave the gap between boards even though it looks unfinished at first. It lets water drain through and gives pressure-treated lumber room to expand and contract as its moisture content changes.
Use actual board width, not the nominal size printed at the store. A nominal 2x6 or 5/4x6 board is actually 5.5 in. wide, and a nominal 2x4 is actually 3.5 in., which is what determines real coverage.
Buy stock length close to your actual run rather than always going long. Cutting long boards down to size usually wastes more material than matching stock length, unless you can reuse the offcuts elsewhere.

Frequently Asked Questions

How many deck boards do I need?

Divide the deck's width by one board's width plus the gap between boards to get the number of rows. Multiply by the deck's length to get total linear feet, add a waste allowance, then divide by the stock board length. A 16 ft × 12 ft deck with 5.5 in. boards and a 1/8 in. gap needs about 29 sixteen-foot boards.

How big a gap should I leave between deck boards?

1/8 in. is a common default, especially for pressure-treated lumber installed while still wet, since the boards shrink somewhat as they dry and the gap can close up. Kiln-dried or composite decking sometimes uses a different spacing. Check your specific product's installation instructions.

What's the actual width of a 2x6 or 5/4x6 deck board?

Actual (dressed) width is smaller than the nominal size. A nominal 2x6 or 5/4x6 board is actually 5.5 in. wide, and a nominal 2x4 is actually 3.5 in. wide. This calculator's board width options use actual, not nominal, dimensions, since that's what determines real coverage.

Should I buy longer stock boards even if my deck is shorter?

Not necessarily. Buying stock length close to your actual run length usually wastes less material than buying long boards and cutting them down, unless you can use the offcuts elsewhere (stair treads, a picture-frame border, blocking). Compare the total board count at a couple of stock lengths if your supplier carries more than one option.

Does this include the fasteners to attach the decking?

No. This calculates board count only. Deck screws or hidden fastener clips are typically figured per board per joist crossing, which depends on your joist spacing (a separate input this calculator doesn't take). Budget those as a related but separate material.

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