Decking Calculator
Free decking calculator. Enter deck size and board dimensions to get the number of deck boards, linear feet, joists and screws needed to build a wood or composite deck.
About This Free Online Decking Calculator
Our free decking calculator estimates how much material you need to build a deck. Enter the deck length and width, the board width and the gap between boards, and a waste percentage, and the tool returns the number of deck boards, the total linear feet of board, the joist count at standard 16 in spacing, the screw count and the deck area. It works for pressure-treated wood, cedar and composite boards. Everything runs in your browser — perfect for deck builders and homeowners.
Features of Our Decking Calculator
- Deck board count from area, board width and gap
- Total linear feet of decking
- Joist count at 16 inch on-center spacing
- Screw estimate for the whole deck
- Adjustable waste percentage for cuts
- 100% client-side and private — instant results, no signup
How to Use the Decking Calculator
The Decking Calculator works right in your browser — no signup, no installation. Follow these steps:
- Enter the deck length and width in feet.
- Set the board width and the gap between boards in inches.
- Choose a waste percentage for cuts and offcuts.
- Read off boards, linear feet, joists and screws.
Frequently Asked Questions About Decking Calculator
How many deck boards do I need?
Divide the deck width (in inches) by the board width plus gap to get boards per run, then multiply by the deck length in feet for linear feet, and add 10% waste. The calculator does this and gives the board count, linear feet, joists and screws.
How far apart should deck joists be?
Deck joists are usually spaced 16 inches on center for standard 5/4 boards, or 12 inches for diagonal layouts or thinner composite. The calculator uses 16 inch spacing for the joist count.
How much gap should I leave between deck boards?
About 1/8 to 1/4 inch (0.125 to 0.25 in) for drainage and expansion. Pressure-treated wood can be gapped slightly more as it dries. Enter your gap and the calculator includes it in the board count.
How many screws do I need for a deck?
Figure roughly two screws per joist at every board intersection — for 16 in spacing that is about 350 screws per 100 sq ft. The calculator scales this to your deck size.
Is this decking calculator free?
Yes, completely free with no signup. All estimates run in your browser — nothing is uploaded or tracked.
Why Choose the Decking Calculator?
The Decking Calculator turns your measurements into real material estimates — bags, yards, sheets or gallons — so you buy the right amount the first time. It calculates instantly in your browser and never stores your project details.