Decking Calculator
Calculate exactly how many boards, joists, screws, and fixings you need for your garden deck. Get a full materials list and cost estimate in seconds — for timber, composite, standard, diagonal, and herringbone layouts.
Deck Dimensions & Options
Enter your details above and click Calculate to see your results
How It Works
Our decking calculator walks you through three straightforward steps to produce an accurate, itemised shopping list for your deck project. Whether you are building a small patio platform or a large wraparound garden deck, the process is the same.
Enter Your Dimensions
Measure your deck area in metres and enter the length and width. For L-shaped decks, add a second section. Choose between rectangle or L-shape layouts to match your garden space. Our calculator handles irregular shapes by splitting them into manageable rectangular sections.
Choose Your Materials
Select your board type — from budget-friendly treated softwood through to premium composite decking. Pick your preferred layout pattern (standard, diagonal, or herringbone) and the calculator automatically adjusts waste allowances. Set joist spacing to match your board manufacturer's recommendations.
Get Your Shopping List
Hit Calculate and receive a complete bill of materials: decking boards, joists, bearers, posts, screws, and weed membrane. Every item includes an estimated cost based on typical UK supplier pricing. Export the results as a PDF to take to the timber yard or share with your builder.
Why Use This Calculator
Accurate Estimates
Calculates boards, joists, bearers, posts, screws, and membrane based on industry-standard spacing and sizing. Accounts for waste by layout pattern — 10% for standard, 15% for diagonal, 20% for herringbone.
Instant Results
Get a complete materials list and cost breakdown in seconds. No waiting, no sign-up required. Just enter your deck dimensions and choose your options.
Private & Secure
Every calculation runs entirely in your browser. We never store your project details on any server. Your data stays on your device — save and load locally whenever you return.
PDF Export
Download a print-ready PDF of your results including a full materials shopping list, cost breakdown, and input summary. Take it to the timber yard or share with your builder.