Free Fastener Quantity calculator with clear step-by-step results.
Fasteners are counted from spacing along a run, and the count is one more than the number of gaps: a 3 m rail at 300 mm centres has 10 gaps but 11 screws. Multiply by the number of rows — two per joist, three per stud, four per bracket — and add a loss allowance for the screws that strip, snap or roll under the deck.
Fasteners per row
Per row = floor(run length in mm ÷ spacing) + 1
Purchase quantity
To buy = ceil(per row × rows × (1 + loss allowance))
Fastener spacing, type, length and corrosion rating are governed by the structural design and the manufacturer's fixing schedule. Never substitute a calculated count for a specified fixing pattern in load-bearing or safety-critical work.
Spacing describes the gaps between fasteners, and a run with n gaps has n+1 fixing points because both ends need one. Skipping the +1 quietly under-orders on every run.
It depends on the fixing, not on this calculator. Follow the manufacturer's or code-specified schedule — for example 150 mm on sheathing edges and 300 mm in the field is a common pattern for board fixings.
Screws snap in hardwood, heads strip, and small fasteners simply get lost on site. A part box left over is much cheaper than a second trip.