FEMA recommends

5 square feet per person

4' x 4' - 3 person

4' x 6' - 5 person

4' x 8' - 6 person

6' x 6' - 7 person

4' x 10' - 8 person

6' x 8' - 9 person

6' x 10' - 12 person

8' x 8' - 12 person

8' x 10' - 16 person

We have several other sizes in 8" increments available