Roof batten calculator: courses, metres and lengths
The calculator needs JavaScript. The worked example, formula and figures below show exactly how it works, so you can do the sum yourself. A guide, not advice. Check your supplier's or maker's figures before ordering.
Short answer
Worked example
| You enter | Value |
|---|---|
| Rafter length on the slope | 4 m |
| Batten gauge | 250 mm |
| Roof width | 6 m |
| Slopes | 2 |
| Extra battens at the eaves per slope | 1 |
| Batten lengths you can buy | 4.8 m |
| Allowance per piece | 100 mm |
| Counter-battens | No |
Order: 46 × 4.8 m battens (204.0 m)
| Result | Value |
|---|---|
| Battens per slope | 17 |
| Courses per slope (before eaves battens) | 16 |
| Batten | 204 m |
| Lengths to buy | 46 |
| Length | Cut into | Offcut |
|---|---|---|
| 1 (4.8 m) | Slope 1, batten 1 (part 1 of 2): 4.8 m | 0 m |
| 2 (4.8 m) | Slope 1, batten 2 (part 1 of 2): 4.8 m | 0 m |
| 3 (4.8 m) | Slope 1, batten 3 (part 1 of 2): 4.8 m | 0 m |
| 4 (4.8 m) | Slope 1, batten 4 (part 1 of 2): 4.8 m | 0 m |
| 5 (4.8 m) | Slope 1, batten 5 (part 1 of 2): 4.8 m | 0 m |
| 6 (4.8 m) | Slope 1, batten 6 (part 1 of 2): 4.8 m | 0 m |
| 7 (4.8 m) | Slope 1, batten 7 (part 1 of 2): 4.8 m | 0 m |
| 8 (4.8 m) | Slope 1, batten 8 (part 1 of 2): 4.8 m | 0 m |
| 9 (4.8 m) | Slope 1, batten 9 (part 1 of 2): 4.8 m | 0 m |
| 10 (4.8 m) | Slope 1, batten 10 (part 1 of 2): 4.8 m | 0 m |
| 11 (4.8 m) | Slope 1, batten 11 (part 1 of 2): 4.8 m | 0 m |
| 12 (4.8 m) | Slope 1, batten 12 (part 1 of 2): 4.8 m | 0 m |
| 13 (4.8 m) | Slope 1, batten 13 (part 1 of 2): 4.8 m | 0 m |
| 14 (4.8 m) | Slope 1, batten 14 (part 1 of 2): 4.8 m | 0 m |
| 15 (4.8 m) | Slope 1, batten 15 (part 1 of 2): 4.8 m | 0 m |
| 16 (4.8 m) | Slope 1, batten 16 (part 1 of 2): 4.8 m | 0 m |
| 17 (4.8 m) | Slope 1, batten 17 (part 1 of 2): 4.8 m | 0 m |
| 18 (4.8 m) | Slope 2, batten 1 (part 1 of 2): 4.8 m | 0 m |
| 19 (4.8 m) | Slope 2, batten 2 (part 1 of 2): 4.8 m | 0 m |
| 20 (4.8 m) | Slope 2, batten 3 (part 1 of 2): 4.8 m | 0 m |
| 21 (4.8 m) | Slope 2, batten 4 (part 1 of 2): 4.8 m | 0 m |
| 22 (4.8 m) | Slope 2, batten 5 (part 1 of 2): 4.8 m | 0 m |
| 23 (4.8 m) | Slope 2, batten 6 (part 1 of 2): 4.8 m | 0 m |
| 24 (4.8 m) | Slope 2, batten 7 (part 1 of 2): 4.8 m | 0 m |
| 25 (4.8 m) | Slope 2, batten 8 (part 1 of 2): 4.8 m | 0 m |
| 26 (4.8 m) | Slope 2, batten 9 (part 1 of 2): 4.8 m | 0 m |
| 27 (4.8 m) | Slope 2, batten 10 (part 1 of 2): 4.8 m | 0 m |
| 28 (4.8 m) | Slope 2, batten 11 (part 1 of 2): 4.8 m | 0 m |
| 29 (4.8 m) | Slope 2, batten 12 (part 1 of 2): 4.8 m | 0 m |
| 30 (4.8 m) | Slope 2, batten 13 (part 1 of 2): 4.8 m | 0 m |
| 31 (4.8 m) | Slope 2, batten 14 (part 1 of 2): 4.8 m | 0 m |
| 32 (4.8 m) | Slope 2, batten 15 (part 1 of 2): 4.8 m | 0 m |
| 33 (4.8 m) | Slope 2, batten 16 (part 1 of 2): 4.8 m | 0 m |
| 34 (4.8 m) | Slope 2, batten 17 (part 1 of 2): 4.8 m | 0 m |
| 35 (4.8 m) | Slope 1, batten 1 (part 2 of 2): 1.4 m; Slope 1, batten 2 (part 2 of 2): 1.4 m; Slope 1, batten 3 (part 2 of 2): 1.4 m | 0.6 m |
| 36 (4.8 m) | Slope 1, batten 4 (part 2 of 2): 1.4 m; Slope 1, batten 5 (part 2 of 2): 1.4 m; Slope 1, batten 6 (part 2 of 2): 1.4 m | 0.6 m |
| 37 (4.8 m) | Slope 1, batten 7 (part 2 of 2): 1.4 m; Slope 1, batten 8 (part 2 of 2): 1.4 m; Slope 1, batten 9 (part 2 of 2): 1.4 m | 0.6 m |
| 38 (4.8 m) | Slope 1, batten 10 (part 2 of 2): 1.4 m; Slope 1, batten 11 (part 2 of 2): 1.4 m; Slope 1, batten 12 (part 2 of 2): 1.4 m | 0.6 m |
| 39 (4.8 m) | Slope 1, batten 13 (part 2 of 2): 1.4 m; Slope 1, batten 14 (part 2 of 2): 1.4 m; Slope 1, batten 15 (part 2 of 2): 1.4 m | 0.6 m |
| 40 (4.8 m) | Slope 1, batten 16 (part 2 of 2): 1.4 m; Slope 1, batten 17 (part 2 of 2): 1.4 m; Slope 2, batten 1 (part 2 of 2): 1.4 m | 0.6 m |
| 41 (4.8 m) | Slope 2, batten 2 (part 2 of 2): 1.4 m; Slope 2, batten 3 (part 2 of 2): 1.4 m; Slope 2, batten 4 (part 2 of 2): 1.4 m | 0.6 m |
| 42 (4.8 m) | Slope 2, batten 5 (part 2 of 2): 1.4 m; Slope 2, batten 6 (part 2 of 2): 1.4 m; Slope 2, batten 7 (part 2 of 2): 1.4 m | 0.6 m |
| 43 (4.8 m) | Slope 2, batten 8 (part 2 of 2): 1.4 m; Slope 2, batten 9 (part 2 of 2): 1.4 m; Slope 2, batten 10 (part 2 of 2): 1.4 m | 0.6 m |
| 44 (4.8 m) | Slope 2, batten 11 (part 2 of 2): 1.4 m; Slope 2, batten 12 (part 2 of 2): 1.4 m; Slope 2, batten 13 (part 2 of 2): 1.4 m | 0.6 m |
| 45 (4.8 m) | Slope 2, batten 14 (part 2 of 2): 1.4 m; Slope 2, batten 15 (part 2 of 2): 1.4 m; Slope 2, batten 16 (part 2 of 2): 1.4 m | 0.6 m |
| 46 (4.8 m) | Slope 2, batten 17 (part 2 of 2): 1.4 m | 3.4 m |
Show the working
- Courses: (4 m) ÷ 0.25 m, rounded up = 16; + 1 at the eaves = 17 per slope
- Batten: 17 × 2 slopes × 6 m = 204 m
- Lengths: 34 runs of 6 m packed into 4.8 m lengths = 46 lengths (34 joins)
How it works
- Courses per slope = (rafter length − gap at the ridge) ÷ gauge, rounded up
- Battens per slope = courses + extra eaves battens
- Batten (m) = battens per slope × slopes × roof width
- Lengths to buy: each batten run cut from your stock lengths, packed longest first (first-fit decreasing)
- Rafters per slope = roof width ÷ rafter spacing, rounded up, + 1; nails = rafters × battens × slopes × nails per crossing
- Counter-batten (m) = rafters × rafter length × slopes
Batten size, grade and fixings depend on the rafter spacing and the tile or slate: follow the maker's specification and BS 5534.
Our default (adjustable)
These are typical planning figures and our own allowances, not facts about your product. Change any of them in the calculator to match your bag, pack or tin.
| Figure | Our default (adjustable) | Kind | Source |
|---|---|---|---|
| Extra battens at the eaves per slope | 1 battens per slope | Our assumption Not yet checked against the source | Our choice: change it to suit your job brief v2 R3 (test RB1: '16 courses (+1 eaves) per slope'). |
| Allowance per piece | 0.1 m | Our assumption Not yet checked against the source | Our choice: change it to suit your job Allowance per piece for squaring ends and mitres (brief v2 FL2). |
Regulations and standards
- BS 5534 (slating and tiling): batten sizes, gauge and fixings from the tile or slate maker
Explained: BS 5534 (slating and tiling).
Our checks use the guidance for England unless a badge says otherwise. Wales, Scotland and Northern Ireland have their own rules: check the source for where you live.