IKEA's size guide gives 1 to 2 people 6 to 8 place settings and 3 to 4 people 10 to 12. It's a rule of thumb, and most 24-inch machines hold 12 to 16 by Abt's count. If you have the gap, a couple can run a big one less often.
About 5 cu ft per adult, within 4 to 6. Sharp, Reviewed and Abt all land there. Liebherr says 2 to 2.5 per person, so treat none of this as settled. Measure the gap and the doorway before you pick a number.
AHAM's rule is a smoke CADR of at least two-thirds of the floor area, so 200 for a 300 sq ft (28 m²) room with an 8 ft ceiling. For wildfire smoke, AHAM asks for a CADR equal to the full floor area, so 300.
Consumer Reports says at least 4.5 cu ft. Household size is rougher. Retailer Brothers Main gives 1 to 2 people 2.5 to 3.5 cu ft and a family 3.5 to 4.5, and other retailers run higher. I found no standard.
Energy Star gives 20 to 30 pints a day for a slightly to moderately damp space under 2,000 sq ft (186 m²), and 30 to 50 for a wet one. It also says oversizing beats undersizing. Ratings dropped when the test changed for 2020, so an old 50-pint machine and a new 30-pint machine can be equals.
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