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How to measure · Shade sails
How to measure for a shade sail (post to post)
Shade sails confuse people because you measure the gap between posts, then order a sail smaller than that gap. Here's why, and exactly what to measure.
Measure point to point
Measure the straight-line distance between each pair of anchor points — post to post, at the height the hardware will attach, not along the ground. For a triangle that's three spans; for a rectangle, both widths and both lengths (use the smaller if they differ).
Why the sail is smaller than the span
A sail has to be tensioned to stay taut, and that tension comes from turnbuckles and shackles between the sail corner and the post. Those take ~30 cm. So we size the sail down from your span to leave room for the hardware — order the span, and we do that math.
Waterproof? Add a slope
A breathable mesh sail can be near-flat. A waterproof sail must have a pitch — one or two anchor points lower — so rain runs off instead of pooling and stretching it.
FAQ
Do I measure the sail or the posts?
The posts — the span between your anchor points. We size the sail down from that to leave ~30 cm for the tensioning hardware.
Do the posts need to be level?
No — a slope actually helps airflow and drainage. For a waterproof sail you want a deliberate pitch so rain runs off.