Quick answer: Measure the distance between your mounting points, then subtract 1 to 3 ft from each side to leave room for hardware. The result is the largest sail size that will fit. For example, if your posts are 14 ft by 18 ft apart, a 12' x 16' sail leaves about 1 ft at every corner for turnbuckles and snap hooks.
Choosing a shade sail size is not about the area you want to cover. It is about the space between the points you can attach to. A sail is pulled tight between its corners, so it always ends up smaller than the space around it. This guide shows how to work out the right size and which stock sizes we carry.
Step 1: Measure between your mounting points
Pick a solid anchor for every corner: a wall, a strong post or a dedicated shade sail pole. Measure the straight-line distance between each pair of points. For a square or rectangle, also measure both diagonals. If the diagonals are different, your space is not square and a custom size may fit better.
Step 2: Subtract room for hardware
Every corner needs a fixing and a tensioner, so you need a gap between the sail corner and the anchor. We recommend leaving 0.5 to 1.5 ft at each corner. That means the sail should be about 1 to 3 ft shorter than the space on each side.
| Distance between mounting points | Sail size that fits | Room left per corner |
|---|---|---|
| 10 ft x 12 ft | 8' x 10' | about 1 ft |
| 12 ft x 15 ft | 10' x 13' | about 1 ft |
| 14 ft x 18 ft | 12' x 16' | about 1 ft |
| 16 ft x 22 ft | 14' x 20' | about 1 ft |
| 14 ft x 14 ft | 12' x 12' | about 1 ft |
A little extra room is fine because the turnbuckles take up the slack. A sail that is too big is the real problem: it cannot be tensioned, so it sags and flaps in the wind.
Watch: how to measure for a shade sail
This 2-minute video shows how a Super Ring shade sail is built and walks through another measuring example: mounting points 19 ft by 19 ft apart fit a 17' x 17' sail, with the gap at each corner filled by adjustable hardware.
Watch on YouTube · Shop Super Ring shade sails
Step 3: Match the size to the space
| Space | Typical sail | Tip |
|---|---|---|
| Small patio or balcony | Square 10' x 10' or a right triangle | A right triangle fits neatly into a corner against the house. |
| Dining or lounge area | Rectangle 10' x 13' to 12' x 16' | Choose a waterproof sail if you want to stay dry. |
| Deck or large patio | Rectangle 14' x 18' to 16' x 20' | Or overlap two triangles for a modern look. |
| Pool, driveway or play area | Large square or rectangle | Large spans need heavy-duty 260 GSM sails with steel cable edges. |
ShadeMart stock sizes
- Standard rectangle: 14 sizes from 8' x 10' to 16' x 20'.
- Standard square: 7 sizes from 10' x 10' to 26' x 26'.
- Waterproof square: 12 sizes from 4' x 4' to 14' x 14'.
- Triangle and right triangle: many sizes for corners and layered designs.
Sizes are measured corner to corner, from D-ring to D-ring.
When to choose a custom size
Order a custom shade sail if no stock size leaves 0.5 to 1.5 ft at each corner, if your diagonals are not equal, or if your space is very large. We make custom sails in our La Puente, California workshop in 1–3 business days and ship them within 3–7 business days. For more help, read standard size or custom size shade sail.
Frequently asked questions
Should the shade sail be the same size as my space?
No. The sail must be smaller than the space between your mounting points so there is room for hardware and tension. Leave 0.5 to 1.5 ft at each corner.
Are shade sail sizes measured edge to edge?
Our sizes are measured corner to corner, from D-ring to D-ring. Curved edges mean the fabric between the corners is a little narrower.
What size shade sail do I need for a 12 x 16 ft patio?
If your mounting points sit at the corners of the patio, about 12 ft by 16 ft apart, a 10' x 13' sail will usually fit. If your posts are further out, about 14 ft by 18 ft apart, you can use a 12' x 16' sail.
Can I join two sails to cover a bigger area?
Yes. Overlapping two or three sails at different heights covers a large area and looks great. Each sail still needs its own anchors.
Not sure which size fits? Call us at 888-777-2538 or send us your measurements and we will recommend a size.
