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How the calculator works

Over a dining table, the canopy should reach 2 feet past the table on every side. That keeps people in the shade when they sit back, and it still works when the sun is not directly overhead. So the umbrella should be about 4 feet wider than the table.
Over a seating area, 1 foot past the seats on every side is enough, because the seats already mark the edge of where people are.
The result is rounded up to a size stores sell: 6, 7.5, 9, 10, 11 or 13 feet.

Quick size guide

Bistro table up to 24 inches: 6 ft umbrella
Table up to 42 inches, 2 to 4 seats: 7.5 ft umbrella
Table up to 60 inches, 4 to 6 seats: 9 ft umbrella
Table up to 72 inches, 6 seats: 10 ft umbrella
Table up to 84 inches, 6 to 8 seats: 11 ft umbrella
Table up to 108 inches, 8 to 10 seats: 13 ft umbrella, or a rectangular one
Longer tables: two umbrellas

How heavy the base should be

The base matters more than the canopy. An umbrella that tips over breaks itself and whatever it lands on.

Through a table: about 5 lb for every foot of canopy, and never less than 30 lb. The table helps hold the pole.
Freestanding: about 10 lb for every foot of canopy, so 75 lb for a 7.5 ft umbrella and 90 lb for a 9 ft one.
Cantilever (offset): 200 lb or more. The weight hangs to one side, so these need a filled or weighted cross base.

These are minimums for a sheltered patio. In an open or windy spot, go one step heavier, and close the umbrella when you are not under it.

Round or rectangular

A round umbrella suits a round or square table. Over a long table, a rectangular canopy covers the ends without hanging far over the sides, which matters on a narrow patio. The calculator points this out when your area is at least one and a half times longer than it is wide.

When an umbrella is not enough

If the result is over 13 feet, look at a shade sail, a pergola or a gazebo. We compare eleven options, with what each one costs in space and effort, in patio shade ideas.

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