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Right angle triangle shade sail

Updated: 16.10.2026

The patio meets the house on two walls, and you need to decide whether a right angle triangle shade sail will sit in that corner or whether equal sides are the honest shape. The title 3 × 4 × 5 m is a right angle only on paper. Curved edges stop a clean 90-degree fit against the brick. This page is from the Products Compared editorial team, updated on 16 October 2026. We compared the side lengths in the [triangle shade sail comparison](/hub/sun-shades/triangle-shade-sail). We did not survey your patio. A qualifying purchase can earn us a commission at no extra cost to you. Who rates which listing is on the [best triangle shade sail](/hub/sun-shades/triangle-shade-sail/sub/triangle-shade-sail-best) page.

The patio meets the house on two walls, and you need to decide whether a right angle triangle shade sail will sit in that corner or whether equal sides are the honest shape.

Our top picks

MissYolo MissYolo 3 x 3 x 4.3 m triangle

Best overall

MissYolo MissYolo 3 x 3 x 4.3 m triangle
7.2/10about £11.90
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IOAOI IOAOI 3 x 4 x 5 m triangle

Alternative

IOAOI IOAOI 3 x 4 x 5 m triangle
7.6/10about £29.99
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KAHEIGN KAHEIGN 3 x 3 x 3 m triangle

Rank 3

KAHEIGN KAHEIGN 3 x 3 x 3 m triangle
8.0/10about £14.99
View offer
On this page
  1. 1.Start from the three spans you can actually use
  2. 2.Equal sides for a simple three-point span
  3. 3.A 3 × 4 × 5 m sail is a right angle until the edge curves
  4. 4.When a rectangle is the honest alternative

Start from the three spans you can actually use

Measure between the fixing points, not along the slabs. A triangle needs three anchors and nothing more, which is why it suits a corner that does not have a fourth post. Clara Shade Sails and Shade Sail Boutique both describe a triangle as a three-anchor shape that covers less than a four-corner sail of a similar overall size. Write the three lengths down. If they are nearly equal, you are in equilateral territory. If they read about 3 m, 4 m and 5 m along a square corner, you are looking at a right-angle title. If two are equal and the third is longer, but not a 3-4-5, you are in the scalene group in this set. The tension gap is set out on the triangle shade sail buying guide.

Equal sides for a simple three-point span

Choose equal sides when the three measurements match. In this set the equilateral sails are KAHEIGN at 3 × 3 × 3 m, about £14.99, both HEYOMART colourways at 2.5 × 2.5 × 2.5 m, about £13.99, DAJAVE at 3 × 3 × 3 m, about £19.99, and YOUNTHYE at 3 × 3 × 3 m, about £23.99. A straight-sided equilateral triangle of 3 m has about 3.9 square metres of cloth. The 2.5 m size is a smaller patch again, about 2.7 square metres if you use the same straight-side formula. Curved edges make the shade on the ground smaller than that cloth area. HEYOMART states a tolerance of about 4–6 inches a side.
MissYolo MissYolo 3 x 3 x 4.3 m triangle

Testsieger

MissYolo MissYolo 3 x 3 x 4.3 m triangle
7.2/10about £11.90
View offer

A 3 × 4 × 5 m sail is a right angle until the edge curves

A triangle with sides 3 m, 4 m and 5 m is a right angle if the edges are straight, because 3² + 4² = 5². The area of that straight triangle is 6 square metres, which is why the cloth looks generous next to a 3 m equilateral sail. IOAOI is titled 3 × 4 × 5 m, pale yellow, about £29.99. The larger MissYolo is the other 3 × 4 × 5 m title, dark grey, about £18.67. Both are the listings to open when your corner really is about those three lengths. They stop being a set square once the hem curves, and an IOAOI review says the sides did not sit on a 90-degree wall.

When a rectangle is the honest alternative

A triangle is the right tool when you have three strong points and you can live with less cover than a four-sided sail of a similar overall size. It is the wrong tool when you want the whole square of a patio in shade, or a straight edge tight into a 90-degree corner. Four anchors and a rectangle or a square sail cover more of that footprint. shade-sails.co.uk often steers buyers towards four attachment points for that reason. If your garden already has a pergola with four corners, forcing a triangle across three of them leaves a wedge of sun you will notice at tea time. Four corners belong on the sun sail comparison, not on a three-point patio.

Common questions

Is a 3 × 4 × 5 m sail a right angle?
It is a right angle if the sides are straight, because those lengths satisfy the 3-4-5 rule. The ready-made sails titled that way in this set also use curved edges. A curve means the cloth will not reproduce a set-square corner once it is hanging. Treat right angle as the side lengths, and then read the hem.
Will it fit a square corner of the house?
It will shade a square corner if your spans are near 3 m, 4 m and 5 m and you leave a tension gap. It will not lie flush to both walls. An IOAOI review says the curved sides did not match a 90-degree wall. Expect a strip of sun along the brick unless you commission a sail cut to that reveal.
When is a 3 × 3 × 3 m sail the better shape?
When all three fixing spans are about the same, a little longer than 3 m so the ropes have room. A straight 3 m equilateral sail has about 3.9 square metres of cloth, less once the edges curve. It is the better shape for a simple three-point patio. It is a poor fit on a 3-4-5 corner.
What does a curved edge do to a right angle?
The curve is there so tension can pull the edge straighter and lift the middle. That reduces the shaded area compared with the post span, and it rounds off the 90-degree corner the side lengths suggest. You gain a tighter centre. You lose a neat line against the wall.
Which loaded sails are which shape?
Equilateral: KAHEIGN, both HEYOMART colours, DAJAVE and YOUNTHYE. Right-angle titles: IOAOI and the MissYolo 3 × 4 × 5 m sail. Longer third side, not a 3-4-5: RICHIE, MOXTOYU, the smaller MissYolo and Sowoxdme. Check the size line on the day, because some bullets mention other lengths as options.

Related pages

How to install a triangle shade sail

Triangle shade sail

Best triangle shade sail: span, reviews and the box

Triangle shade sail buying guide: measure the span

Waterproof triangle shade sail: read the small print

Sources

Public UK sources used for this comparison. Listing prices, stars and review counts are the amazon.co.uk figures saved in the comparison files, not a live re-check.

  1. NHS — sunscreen and sun safety (retrieved 16.10.2026)
  2. GOV.UK — ultraviolet radiation frequently asked questions (retrieved 16.10.2026)
  3. Class E, England — buildings incidental to a dwellinghouse (retrieved 16.10.2026)
  4. Greater Cambridge planning — external shading (retrieved 16.10.2026)
  5. Consumer Rights Act 2015, section 9 (retrieved 16.10.2026)
  6. CAP Code rule 3.7 — objective claims (retrieved 16.10.2026)
  7. Clara Shade Sails — installation guide (retrieved 16.10.2026)
  8. Shade Specialists — shade sail installation instruction (retrieved 16.10.2026)