Fence Post Spacing Calculator — Posts, Panels & Postcrete

Our fence post calculator works by dividing your total fence run length by the panel width to determine the number of panels, then adds one extra for the end post.

The formula

Number of panels = Total length ÷ Panel width (rounded up)

Number of posts = Panels + 1

Postcrete bags = Posts × bags-per-post (default 2)

The default of 2 × 20kg bags per post is a conservative planning figure. A 20kg bag of Postcrete yields roughly 0.01 m³ (10 litres), so a 100mm post in a standard 200 × 600mm hole needs about 1 bag; allow 2 for wider 300mm holes, gate posts or exposed sites. Adjust the bags-per-post figure in advanced options to suit your hole size.

UK standard sizes

• Standard panel width: 1.83m (6ft) — most common UK size
• Post size: 75mm × 75mm or 100mm × 100mm
• Post length: 2.4m (8ft) for 6ft panels (600mm in ground)
• Postcrete: 1-2 × 20kg bags per post
• Gravel boards: 1.83m × 150mm per panel bay

Note: If your fence run is not an exact multiple of the panel width, you may need to cut the last panel to fit. The calculator rounds up to whole panels. For corners and direction changes, add an extra post at each corner.