Home › Building Projects › Deck Board Calculator
Deck Board Calculator
Deck boards, linear feet and a screw estimate for a rectangular deck.
Decking boards are bought by the piece in fixed lengths, but decks are measured in square feet — and the conversion depends on board width and the gap between boards. This calculator works out how many boards run across your deck, the linear feet that represents, and a fastener estimate so the hardware is on site before the first board goes down.
The calculation assumes boards run along the length of the deck, the most common layout. It includes the standard small gap that lets timber move and water drain — pack that gap out of the design and the board count will be wrong, because the gaps together add up to several whole boards across a wide deck.
Calculate
Enter your measurements — the estimate updates as you type.
Estimates for planning and buying only. Product coverage varies by brand — check the label of the exact product you buy.
How to use this calculator
- Decide the board direction first — boards should usually run away from the house or along the longer dimension for fewer joints.
- Measure the deck frame, not the old surface you are replacing.
- Use the actual face width of your board; a '6 inch' deck board is really 5.5 inches wide.
- Calculate, then plan butt joints if your deck is longer than the longest board you can buy — stagger them across different joists.
How deck boards are calculated
Rows = deck width in inches / (board width + gap). Each row runs the full deck length, so linear feet = rows x length, plus waste. The screw estimate assumes joists every 16 inches along the length and two screws at every board-to-joist crossing. Hidden-clip composite systems use roughly one clip per crossing instead — the crossing count is the same.
Common mistakes to avoid
- Using the nominal board width (6 inches) instead of the real 5.5 inches, which understates the board count by about two full boards on a typical deck.
- Butting boards tight with no gap — the first wet season swells them into each other and traps water.
- Staggering nothing: lining all butt joints up on one joist creates a weak, visibly striped line across the deck.
Frequently asked questions
Which way should deck boards run?
Along the direction that gives the fewest joints and the best drainage away from the house. On a house-attached deck, boards running out from the wall shed water off the free edge.
How far apart should joists be?
Sixteen inches on centre is standard for timber boards laid straight. Diagonal layouts and many composite boards need 12 inches — check the board manufacturer's specification before building the frame.
How many screws does a deck take?
Roughly two screws at every crossing of board and joist. The calculator estimates crossings from 16-inch joist spacing; a mid-size deck commonly lands between 400 and 700 screws.
Should I leave the ends of boards overhanging to trim later?
Yes — running boards long and snapping a chalk line to cut them in place is the reliable way to get a perfectly straight deck edge.
Related calculators
Concrete Bag Calculator
Cubic yards of concrete and 40, 60 and 80 lb bags for a slab or footing.
Open calculator →Fence Calculator
Panels, posts, rails and concrete for a straight panel fence run.
Open calculator →Brick Calculator
Bricks and mortar bags for a wall, by brick type and wall size.
Open calculator →