Decking Calculator

Boards, joists, posts, screws and clips.

Inputs

Got a bay window or conservatory? Set it out in Setting Out & Levels → Bays & conservatories. It carves the bay footprint out of the paved area and adjusts the wall run, then hands the corrected figures back here.

Decking type

Project location

Length(m)

Width(m)

Deck height(mm)

6 advanced inputs hidden. Switch to Advanced to fine-tune.

Confidencehigh· 78Complexitymedium· 34

Boards required: 32

Heads-up: Softwood decking uses joist centres at 400 mm, screws into pre-drilled pilot holes, and needs a 150 mm ventilation gap under the deck so it can breathe. Why it matters: Sealed-under decking traps moisture, rots joists, and harbours rats — keep the air moving.

5 detailed breakdowns hidden — switch to Advanced for the full breakdown.

This app provides general UK guidance and material estimates only. It is not legal, planning, engineering or building-control advice. Always confirm requirements with your local planning authority, building control, utility providers, manufacturers or qualified professionals.