Deck materials calculator
Works for a rectangular deck with boards running parallel to the house and joists spanning out from it. Change board width, joist spacing or footing size to match your plan and permit drawings.
Materials takeoff
Deck Materials Calculator · https://estimahome.com/deck-calculator/
Deck length (parallel to house): 16 ftDeck depth (out from house): 12 ft
- Deck area
- 192 sq ft
- Board rows
- 26
- Decking
- 416 lin ft
- Footing concrete
- 7.07 cu ft
| No. | Item | Qty | Unit | Unit cost | Amount |
|---|---|---|---|---|---|
| 1 | Deck boards, 16 ft | 29 | ea | $18.00 | $522.00 |
| 2 | Joists, 12 ft span | 13 | ea | $22.00 | $286.00 |
| 3 | Deck screws (676 pcs) | 2 | box | $38.00 | $76.00 |
| 4 | Posts | 3 | ea | $25.00 | $75.00 |
| 5 | Concrete, 80 lb bags | 12 | bag | $6.50 | $78.00 |
- Subtotal
- $1,037.00
- Likely range
- $881.45 – $1,192.55
- Not included: beams, ledger, rim joists, hangers, post bases, stairs, railings.
- Joist size, span and footing size are set by your local code. Check before you buy.
Buy these materials
- 29 deck boards (16 ft)Amazon search for deck boards (16 ft) (opens in new tab)
- 13 joists (12 ft span)Amazon search for joists (12 ft span) (opens in new tab)
- 2 boxes of deck screwsAmazon search for boxes of deck screws (opens in new tab)
- 3 postsAmazon search for posts (opens in new tab)
- 12 80 lb bags of concreteAmazon search for 80 lb bags of concrete (opens in new tab)
Links open a store search for each item. Check sizes and grades against your plan.
Quick reference
- A 16 × 12 ft deck with 5.5 in boards and 0.125 in gaps takes 26 rows, about 29 boards at 16 ft with 10% waste.
- Joists at 16 in on center along a 16 ft deck: ⌊16 × 12 ÷ 16⌋ + 1 = 13.
- A 12 in diameter footing 36 in deep holds 2.36 cu ft of concrete, about 4 bags of 80 lb mix.
How it's calculated
⌈x⌉ means round up to the next whole unit; ⌊x⌋ means round down. Every quantity you buy is rounded up.
Board rows = ⌈ depth × 12 ÷ (board width + gap) ⌉Decking linear feet = board rows × deck lengthBoards = ⌈ linear feet × (1 + waste ÷ 100) ÷ board length ⌉Joists = ⌊ length × 12 ÷ joist spacing ⌋ + 1Screws = board rows × joists × 2Screw boxes = ⌈ screws ÷ screws per box ⌉Footings = footing rows × (⌈ length ÷ post spacing ⌉ + 1)Footing concrete (cu ft) = footings × π × (diameter ÷ 24)² × (depth ÷ 12)Bags = ⌈ concrete ÷ bag yield ⌉Cost = Σ (quantity × unit price); range = cost × (1 ± range % ÷ 100)
Worked example
A 16 × 12 ft deck is 192 sq ft. At 5.5 in boards with a 0.125 in gap, each row takes 5.625 in, so 144 ÷ 5.625 rounds up to 26 rows and 416 linear feet. With 10% waste that is 29 boards at 16 ft. Joists at 16 in on center across 16 ft come to 13. Two screws per board per joist is 676 screws, or 2 boxes of 350. One row of footings with posts no more than 8 ft apart needs 3 footings. Each 12 in hole 36 in deep holds 2.36 cu ft, 7.07 cu ft total, which is 12 bags of 80 lb mix. Materials at the default prices: $1,037.00.
Questions
How many deck boards do I need?
Divide the deck depth in inches by board width plus gap to get rows, multiply by deck length for linear feet, add about 10% waste, and divide by board length. Order boards long enough to span between joists without short scraps at the ends.
How many screws per deck board?
Two at every joist the board crosses. For 16 in spacing that works out to roughly 350 screws per 100 sq ft of deck. Hidden clip systems use one clip per board per joist instead.
How far apart should deck joists be?
Usually 16 in on center for wood decking laid square to the joists, 12 in for diagonal decking and many composites. Check the decking manufacturer and your local span tables.
How deep do deck footings go?
Below the frost line, which ranges from a few inches in the South to 4 ft or more up north. Your building department sets the number and usually inspects the holes.
Cite: “Deck Materials Calculator.” EstimaHome, https://estimahome.com/deck-calculator/. Updated 2026-10-20. Formulas in machine-readable form: /api/calculators.json.