Fastener Quantity
Free Fastener Quantity calculator with clear step-by-step results.
About Fastener Quantity
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.
Formulas
Fasteners per row
Per row = floor(run length in mm ÷ spacing) + 1
Purchase quantity
To buy = ceil(per row × rows × (1 + loss allowance))
Worked example
With the default values below, Fastener Quantity returns Fasteners to Buy of 223. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Total run or edge lengthminimum 0 m
- 30 m
- Fastener spacingminimum 10 mm
- 300 mm
- Rows of fastenersminimum 1
- 2
- Loss and rejectsaccepts 0–50 %
- 10 %
Results
- Fasteners to Buy
- 223 pcs
- Fasteners Fitted
- 202 pcs
- Fasteners per Row
- 101 pcs
- Boxes of 100
- 3 boxes
Step by step
- 1Values used
- 2Fasteners per row
- 3Purchase quantity
- 4Fasteners to Buy= 223 pcs
- 5Fasteners Fitted= 202 pcs
- 6Fasteners per Row= 101 pcs
- 7Boxes of 100= 3 boxes
Assumptions and limits
- The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to whole numbers, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
- 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.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
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.
Frequently Asked Questions
Why is it one more than length ÷ spacing?
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.
What spacing should I use?
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.
Why allow 10% for loss?
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.