Formula
Bays are the run length divided by the bay width, rounded up.
Posts are the bays plus one, plus any extra posts you add. Gravel boards match the bays. Fast-set bags are posts times bags per post.
The covered length is bays times bay width. Rounding can carry the fence past the run you measured. Waste is not added again.
Worked example
7 panels cover 12.81 m, which is 0.81 m past a 12 m run.
Posts are bays plus one, plus any extra you add. Fast-set bags are posts times 2. Waste is not added on top of the rounding.
Assumptions
UK bays start at 1.83 m. Australian bays start at 2.4 m.
Two fast-set bags per post is a common shopping assumption for a small timber post, not a specification.
This page does not take a fence height, so it is not a planning calculator.
Checked
Checked 10 November 2026. Wickes lists Forest Garden overlap panels at 1.83 m wide. Bunnings lists ARC wire panels at 2400 mm wide. Two fast-set bags per post is still an assumption for a small timber post, not a yield printed on a bag.
In England, fences over 2 m, or over 1 m next to a highway, can need planning permission. Check GOV.UK.
GuideHow many fence panels and posts do I need?