Work out how many batten rows and running meters of batten you need for a roof, based on eave length, roof width and batten spacing.
The calculator divides the eave length by the batten spacing, rounds up, and adds one extra row for the ridge batten:
Total batten length is found by multiplying the number of rows by the roof width, since each row runs across the entire roof.
Batten spacing is set by the type of roof tile or panel and the manufacturer's guidance. For concrete roof tiles, 30–36 cm is common, while other products can have other requirements — always check the documentation for your product.
Yes, in most constructions counter battens (running lengthwise, in the slope direction) are laid under the roof battens to create a ventilation gap between the underlay and roof covering. This calculator only figures the cross battens, not the counter battens.
The eave length is measured along the roof surface in the slope direction, from the eave (roof edge) to the ridge. This isn't the same as the roof's external slope height — measure along the rafter or truss for an accurate figure.