Fence panel and post calculator

How many fence panels and posts for a straight run, how long the posts need to be, the gravel boards, and how many bags of Postcrete to set the posts.

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Measure the fence line off the drawing with Take-off, put the panels, posts and Postcrete on a purchase order or into your quote from the Book of rates, and save it to the job.

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Worked example

A straight 15 m run of 1.83 m × 1.8 m panels on 75 mm timber posts and gravel boards, with 200 mm × 600 mm post holes:

8 panels and 9 posts

The last panel is cut down to about 1.52 m wide
Posts 75 × 75 mm, 2.7 m long (it needs 2.55 m)
8 gravel boards
9 × 20 kg bags of Postcrete (1 bag a post in a 200 mm wide × 600 mm deep hole)

How the sum works

Each panel sits between two posts, so one bay takes up the panel width plus one post. The calculator fits as many bays as it can into the run, adds the last post, and tells you how wide the last panel needs to be if it doesn't fit exactly. Do each straight run on its own: a corner post starts the next run.

The post length is the panel height, plus 150 mm for a gravel board, plus the depth of the hole, rounded up to the next common length (1.8, 2.1, 2.4, 2.7 or 3 m).

Postcrete

The bags per post come from the table on the Blue Circle Postcrete data sheet, which gives the 20 kg bags for each post size and hole size. Other makers' post-fix mixes differ, so check the table on the bag you buy: Blue Circle Postcrete data sheet.

Before you dig

Find out what is under the ground before you dig post holes: check for buried cables and pipes, and see the guide to safe digging. A fence on a boundary may need the neighbour's agreement, and in England a fence over 2 m high, or over 1 m next to a road or its footpath, usually needs planning permission: see Planning Portal: fences, gates and garden walls.

Guides that go with it

How deep should fence post holes be?Fence post holes are usually dug about 600 mm deep and three times the post width. Post length, gravel boards, Postcrete, concrete posts and wind.How do you avoid hitting buried services when digging?How to avoid hitting buried services, following HSE's HSG47: get plans, scan with a cable locator, mark up, hand dig, and what to do if you strike one.What should I put in a quote for building work?What a quote for building work should say: scope, exclusions, drawings, price and VAT, validity, payment stages, dates, provisional sums and variations.

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