When it comes to determining what size shade sail is best for you, the main factorwill be the space you choose to cover. Shade sail measurements should be taken from corner to corner. You will need to determine the attachment points for your sail. These can be trees, your home, posts, or any sturdy structure.
The shade sails can be slightly smaller than the area you want to cover. A smaller size prevents the sail from blowing around in windy weather and causing structural damage to the attachment points.
It is recommended that you buy 6 inches smaller (leave bigger space for larger shade sails) than the coverage area. （Since the material is stretchable, the final length and width of sails will reduce by 6-12 inches to achieve a better fit.）