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How the calculator works
- It has to stand on the patio. All four posts need solid ground under them, so the frame cannot be larger than the slab or deck.
- It has to cover the people. The calculator uses how many people each standard size seats at a dining table, with room inside the posts to pull the chairs out.
- It picks the smallest size that does both. A structure larger than you need takes light from the house and space from the garden.
What each size holds
- 8 x 8 ft: a bistro set for two
- 8 x 10 or 10 x 10 ft: a table for four, or a loveseat and two chairs
- 10 x 12 ft: a table for six
- 12 x 12 or 12 x 14 ft: a table for eight, or a sectional with a coffee table
- 12 x 16 ft: a table for ten, or dining and lounge side by side
- 12 x 20 ft: twelve people
Lounge furniture needs about the same room as a dining table for the same number of people.
Permits and rules
Many US towns ask for a permit for any structure over 120 square feet, which is anything larger than 10 x 12 feet. Some set the limit at 200. There are usually rules about distance from the property line as well, and homeowner associations have their own. The calculator flags the 120 square foot line, but the local rule is the one that counts.
Pergola or gazebo
A pergola has an open or louvered roof: it gives partial shade and stays light. A gazebo has a full roof: it keeps rain off and is darker underneath. A hardtop gazebo can stay up all year if its snow rating suits your area.
Height and anchoring
Look for at least 7 feet of clearance under the lowest beam. Anchor every post to concrete or to the deck frame, not to pavers or deck boards alone.
Both are compared with umbrellas, sails and awnings in patio shade ideas.
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