In hot summers, shade cloth keeps lettuce from bolting, stops tomatoes scalding and gives seedlings a break from the afternoon sun. Getting the size right depends on how you fit it.
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Choose a flat frame, hoops or a frame with sides down, enter the area and height, and the calculator gives the cloth size to buy, the clips around its edge and a guide to the shade percentage.
Flat: (length + 2 × overhang) × (width + 2 × overhang) Hoops: (length + 2 × overhang) × (hoop arc + 2 × overhang) Sides down: (length + 2 × height) × (width + 2 × height) clips = ceil(cloth perimeter ÷ clip spacing)
Over hoops, the cloth follows the arc of the hoop, which is calculated as half an ellipse, like the row cover calculator. With sides down, the cloth drops the full frame height on every side.
A 3 × 1.2 m bed with a flat frame and 30 cm overhang on every side needs a 3.6 × 1.8 m cloth (6.48 m²), held by 18 clips at 60 cm spacing. A 50% shade cloth is a common choice for summer salad greens.
Many growers use 30–50% shade cloth for vegetables in hot climates: lower for fruiting crops like tomatoes and peppers, higher for lettuce and greens.
Add the overhang to each side of the area for flat frames, or the hoop arc or frame height for covers that drape down. This calculator does the maths for each case.
Yes, it cuts direct sun and leaf temperature. Keep sides open for airflow to avoid trapping heat.
It is best supported above the plants on hoops or a frame so air can move and leaves are not scorched where they touch.