Fence Panel and Post Calculator (Lap, Closeboard and Privacy Panels)

Add the straight lengths together and leave out any gate openings. A run that turns a corner is still one run; enter its corners below. Two lengths of fence that do not meet, such as one down each side of a garden, are two runs, because each starts and ends on its own post.

Tools needed: Tape measure or measuring wheel, String line and pegs

A fence down one side, across the back and up the other side has two corners. Each straight is set out from its own corner post, so it ends in its own part panel; the page allows one more panel for each corner rather than assuming the cut panels can be shared. The corner post itself is already in the post count: concrete and vinyl systems sell it as a separate corner post, which is why it is listed.

One continuous fence, corners and all, is one run. Freedom's planning sheet counts one post a panel plus one end post to finish each run, so every extra run adds one post and, like a corner, one more panel for its own part panel at the end.

Use the measured or catalogue width, not the name. A UK six-foot panel is 1.83 m (72 in) wide, and Grange makes its lap panels 183 cm (72 in) wide at every height. A US panel sold as 6 by 6 or 6 by 8 can be narrower than its name: Freedom's Brighton 6x6 is 65.5 in (1.664 m) wide.

The post's own width sits between every pair of panels, so it is added to the panel to give the post centres. Grange's set-out drawing uses 75 mm (2.95 in) posts, which put 1.83 m (6 ft) panels at 1.905 m (6 ft 3 in) centres; on 100 mm (3.94 in) posts the same panels set out at 1.93 m (6 ft 4 in). Freedom's vinyl posts are 5 in (127 mm) square. The post also decides the concrete: Tarmac's Postcrete table has rows for 75 mm (2.95 in) and 100 mm (3.94 in) square posts only. The size of post a fence needs is the maker's call for its height and exposure, not this page's.

Freedom sets its posts at the panel width plus 3/8 in (9.5 mm) for the brackets plus the post width. Grange's drawing allows nothing: the panel sits between the posts in its clips. If a maker gives the post centres directly, enter the difference between those centres and the panel plus the post here.

Count what actually meets the post. Freedom slides a bracket onto each of its Brighton panel's three rails, top, middle and bottom, so three a side, and that is the figure the page opens on. No UK maker's count was found: Grange hangs its panels on Metclips nailed to the posts without giving a number, so for a UK panel use the clip maker's count for the panel's height.

Used only to work out the shortest post. Grange lap panels come 0.9 m (2.95 ft), 1.2 m (3.94 ft), 1.5 m (4.92 ft) and 1.8 m (5.91 ft) high, and Freedom's Brighton 6x6 is 68 in (1.73 m) high.

Makers differ, so take the figure from the one whose posts you use. Grange puts a quarter of the post's length in the ground, 600 mm (23.6 in) of a 2.4 m (7.87 ft) post. Tarmac's Postcrete guide and Quikrete both dig to a third of the post's height, and Tarmac's table gives bags for holes from 450 to 750 mm (17.7 to 29.5 in) deep. Freedom digs to the frost line over gravel; with a 36 in (914 mm) frost line that is 24 in (610 mm) of post in concrete on 12 in (305 mm) of gravel, and the gravel is not part of this depth. Where the ground freezes, the local frost depth governs whatever the rule.

Grange asks for every timber panel to be kept off the ground so it does not rot, with gravel boards filling the gap on level and sloping fences, fixed with gravel board clips. The page counts one board a panel and a clip at each post, two a board. A vinyl panel with its own bottom rail, like Freedom's, needs none.

Tarmac's Postcrete guide digs each hole about 3 to 4 times as wide as the post, 225 to 300 mm (8.86 to 11.8 in) for a 75 mm (2.95 in) post, and its data sheet gives bags for holes from 150 to 300 mm (5.91 to 11.8 in) wide; the metric page opens on 250 mm (9.84 in). Quikrete digs about 3 times the post's diameter, and Freedom digs 10 in (254 mm) for its 5 × 5 in (127 mm) posts and 8 in (203 mm) for 4 × 4 in (102 mm). Quikrete's mix is counted on a round hole this wide, less the post.

Postcrete is Tarmac's ready-to-use post mix, sold in the UK in 20 kg (44.1 lb) bags. Its data sheet gives the bags a post in a table, by the post's size and the hole's width and depth, and states no yield, so the page counts Postcrete only where the post, hole and depth entered are a cell of that table, within 1 mm (0.04 in) of its centimetre or inch heading: 75 mm (2.95 in) and 100 mm (3.94 in) square posts, holes 150 to 300 mm (5.91 to 11.8 in) wide and 450 to 750 mm (17.7 to 29.5 in) deep. Quikrete's Fast-Setting Concrete Mix states a yield for every bag, 0.375 cu ft (10.6 L) for a 50 lb (22.7 kg) bag, 0.45 cu ft (12.7 L) for 60 lb (27.2 kg), 0.41 cu ft (11.6 L) for 25 kg (55.1 lb) and 0.5 cu ft (14.2 L) for 30 kg (66.1 lb), so its bags are the hole less the post over that yield. For the one hole it gives a figure for, a 3 in (76 mm) square post in a 9 in (229 mm) hole 30 in (762 mm) deep, Quikrete says two 50 lb (22.7 kg) bags, and the page takes that.