Roof batten calculator
Running metres, battens and timber volume for roof battening.
Fill in the fields and the result will appear here automatically.
Estimates running batten length from slope area and the selected spacing. The ratio 1/spacing gives theoretical metres per square metre. Whole pieces round up separately, while timber volume follows the continuous calculated length and section. Purchased-piece volume may therefore exceed the displayed volume; end rows and cutting layout need a separate plan.
How it works
Formula and logic
Continuous estimate: running length R = A/s·(1 + w/100), with slope area A in m², spacing s in m and reserve w from 0 to 50%. Pieces = ceil(R/stock length); volume = R·width·height/1,000,000 for a section in mm. This volume follows the continuous calculated length, not every purchased whole piece. End rows, laps, cutting layout and counterbattens are not separately included.
Example
60 m² at 350 mm spacing with 10 % allowance takes 188.57 m, which is 32 six-metre battens.
Fields and units
- Roof area — m²
- Batten spacing — m
- Batten length — m
- Section width — mm
- Section height — mm
- Allowance — %
How to use
- — Enter the roof area — the sloped area, not the footprint.
- — Enter the batten spacing your covering requires.
- — Enter the length and section of the battens you are buying.
- — Add an allowance for cuts and joints.
Method and limitations
- Calculation method
- Formula and logic
- Limitation
- This is a geometric quantity calculation within the described model. It does not establish load capacity, safety or project compliance; check design parameters separately.
FAQ
Should I use the roof area or the floor area?
The roof area — the actual sloped surface. A roof at 30° is about 15 % larger than the building it covers, and the roof area calculator will give you that figure.
What spacing should I use?
Use spacing from the specific covering instructions and design. The field value is an input, not a recommendation. A continuous deck cannot be replaced by battens with an arbitrary spacing.
Why is the volume useful?
It converts the continuous calculated length to m³. For purchased whole pieces use their count and length: 32 pieces at 6 m and 50×50 mm make 0.48 m³. Rounding the piece count adds length beyond the continuous estimate.
Are the counter-battens included?
No. If your roof has a ventilated gap, the counter-battens run the other way at the rafter spacing and are a separate count.
Why round the battens up so aggressively?
Because they are not rounded aggressively — the length is divided by one piece and rounded up once. Every cut leaves a stub, which is what the allowance is for.