How to measure for a straight garden fence

By Measure & Make · Updated 15 October 2026

Start with the complete run

Measure from the outside edge of the first post to the outside edge of the last post. Include the width occupied by those posts. The planner assumes panels sit between posts; it does not add brackets or manufacturer-specific fitting gaps. Use the actual panel width in the product specification rather than relying only on a nominal “six-foot” description.

Write down these measurements

1. Overall length of one straight run, in metres.
2. Actual panel width, in millimetres.
3. Post width measured along the direction of the fence.
4. The number of existing posts you can genuinely reuse in the required positions.
5. The manufacturer’s post-mix allowance for your chosen post and hole dimensions.

Why the last panel sometimes needs a cut

For seven panels you need eight posts, including the two ends. Their widths take up part of the run. The planner finds the smallest panel count that covers the length and shows a cut bay where needed. A short final bay may look awkward; spreading cuts across suitable panels can give a more balanced layout. Some panel designs cannot be shortened without rebuilding the frame.

Worked example: a 12 m run

With 1,800 mm panels and 100 mm posts, seven panels and eight posts cover the run. Six full bays use 10.8 m and the posts use 0.8 m, leaving a 0.4 m final bay. At an example allowance of two bags per new post plus 10% extra, the order allowance is 18 bags. That is an entered allowance, not a universal Postcrete yield.

Check before you buy

• Treat gates and corners as separate design decisions; two runs may share a post.
• Check existing post positions and condition instead of deducting posts only because they are present.
• Confirm the required post length, supports, fixings and ground suitability for the chosen system.
• Enter actual shop prices in the optional budget section. Delivery and fixings need their own allowance.

For product-specific instructions, consult Blue Circle’s Postcrete information. The product guide and site conditions take priority over an illustrative quantity allowance.