Deck Calculator
Work out exactly how many decking boards, joists and screws your deck needs, plus an estimated footing count. Enter your deck length and width, pick a board and framing spec, and get an instant materials list, a live plan-view drawing and an optional cost breakdown — with a printable PDF report.
Material cost estimate (optional)
How to estimate materials for a deck
Three quick steps from deck dimensions to a full materials list.
Measure the length along the house wall and the width the deck extends outward, and note any cut-out for stairs, a hot tub or a tree well.
Choose your decking board width, board length and gap, plus your joist spacing (12, 16 or 24 in on-center).
Get the decking boards, joists, screws and an estimated footing count needed, plus an optional cost estimate.
About the Deck Calculator
A deck build involves ordering several materials that all scale off the same footprint — decking boards, joists, fasteners and footings — and getting any one wrong either stalls the build or leaves you short-handed mid-project. This calculator works out all four from the same set of inputs.
Board count starts with how many rows fit across the deck's width, using your board width plus the gap between boards. Each row runs the full length of the deck, so total linear footage divided by the board length you're buying (8, 10, 12 or 16 ft) gives the number of boards to order.
Joists are spaced along the deck's length at your chosen on-center spacing — typically 12, 16 or 24 inches — with each joist cut to the deck's width. Deck screws are estimated at two fasteners for every point a board crosses a joist, rounded up to full boxes. Concrete footings use a simple planning rule of roughly one footing per 36 sq ft of deck area; the actual count and layout always depends on your beam size, joist span, and local frost depth, so this figure is a starting point for a conversation with your local building department, not a stamped structural plan. The optional cost section adds board, joist and labor prices in eight currencies to turn the materials list into a project budget.
Why use this calculator?
Everything a deck build needs, from board count to a footing planning estimate.
Enter your deck size and get an exact board count in seconds, gap already factored in.
Joist count and cut length from your chosen on-center spacing.
Boards, joists, deck screws and a footing planning estimate in one pass.
Add board, joist and labor prices in eight currencies for a real project budget.
Everything runs in your browser. Nothing you enter is uploaded or stored on a server.
Mix feet, inches, yards, metres, centimetres or millimetres, fully usable on a phone on site.
Related construction tools
Round out the rest of your deck build and outdoor project estimate.
Frequently asked questions
Divide your deck's width by the board width plus the gap to get the number of board rows, multiply by the deck's length to get total linear footage, then divide by the board length you're buying. For a 16×12 ft deck with 5.5 in boards, a 1/8″ gap and 12 ft boards, that works out to roughly 35 boards before waste. Add 5–15% extra for cuts, angled ends and picture-frame borders.
Joists typically run perpendicular to the house and are spaced 12, 16 or 24 inches on-center along the deck's length, with one extra joist at the far end. A 16 ft long deck at 16 in on-center needs about 13 joists, each cut to the deck's width. Always confirm joist spacing and span against your local code and the actual lumber species and size you're using.
This calculator gives a rough planning estimate of roughly one footing per 36 square feet of deck area, with a minimum of four. Actual footing count and spacing depends on your beam size, joist span, local frost depth and soil bearing capacity, so always confirm the final footing layout with your local building department or a structural engineer before digging.
A common rule is two screws (or hidden fastener clips) at every point a board crosses a joist. This calculator multiplies your total board rows by your total joists to get the number of crossings, then doubles it for a screw count, rounded up to full boxes.
5% suits a simple rectangular deck with square-cut ends; 10% is a safe default for most jobs with a few angled cuts or a border; 15% suits complex shapes, picture-frame borders, diagonal patterns or decks with multiple cut-outs. A little extra avoids a mid-project trip back to the lumberyard.