Building calculators for UK projects
Free calculators for decking, fencing and roofing, in metres and millimetres. They show their working and say where their defaults come from.
Decking
- Decking calculator
Boards, joists and fixings for a straight-laid deck, with a plan view and a copyable list.
- Decking board gap calculator
Find the gap that lets whole boards fill the width, so you avoid a thin ripped board.
- Diagonal decking calculator
Boards, cuts, joists and fixings for boards laid at 45 degrees.
- Decking clips and screws calculator
How many hidden clips and screws you need, for your board width and joist spacing.
- Decking subframe calculator
Joists, rim joists, noggins, bearers and posts for the frame under your deck.
- Deck steps calculator
Number of steps, riser height, tread depth and stringers for garden steps.
- Decking cost calculator
Add up boards, frame, labour, steps and handrail using your own prices.
- Decking planning permission checker
Answer a few questions to see whether your deck is likely to be permitted development in England.
Fencing
- Fence panel and post calculator
Panels, posts, gravel boards and post length for a straight run of panel fencing.
- Fence post concrete calculator
Bags of post mix from your hole size, with the range shown when bag yields differ.
Roofing
- Roof pitch calculator
Convert between degrees, percent and rise per 12 inches, then find rise and rafter length.
How the numbers are checked
Each calculator shows its working and lists where its defaults come from. Where we could not confirm a default, the page says so. About and sources.