Sizing Instructions
Many complaints about room air conditioners result
from units that are over-sized or under-sized for a given
area. Over-sized units cool an area before humidity can
be adequately removed, so air feels cold and clammy.
Under-sized units do not sufficiently cool an area.
The following table contains guidelines for properly
sizing a room air conditioner for a given area.
To size unit:
1. Determine size (in square feet) of area to be cooled;
locate square footage in far left column of table
below.
Size of Area
Room below
to be Cooled
attic; insulated
(in square feet)
ceiling above
100
150
200
250
300
350
400
450
500
600
700
800
900
1000
1200
1400
1600
1800
2000
Additional conditions:
· If normal occupancy of area is more than two people, add 600 Btu/hour per person. If normal occupancy is one
person, subtract 600 Btu/hour.
· Add 1200 Btu/hour if area includes a kitchen.
· If room is heavily shaded, subtract 10 percent from total capacity. Increase by 10 percent if area is very sunny.
Required Air Conditioner Cooling Capacity—Btu/hour
3500 to 4000
4000 to 5000
4500 to 5500
5000 to 6000
6000 to 7000
6500 to 7500
7000 to 8000
7500 to 8500
8000 to 9000
9500 to 10500
10500 to 11500
11500 to 13000
12500 to 14000
13500 to 15000
16000 to 17500
18000 to 20000
20000 to 22000
22000 to 24000
24000 to 26000
2. Choose right-hand column showing location of room
in building:
· Room below attic; insulated ceiling above.
· Room with occupied room above.
· Top floor under insulated roof.
3. Follow down right-hand column, reading horizontally
from square footage to find approximate air
conditioner capacity (in Btus per hour) required to
adequately cool designated area.
NOTE: When determining size of unit, also consider
conditions at bottom of table. For best results,
choose air conditioner with cooling capacity
(Btus per hour) closest to, but not exceeding,
estimated size.
Room with
occupied
room above
4000 to 4500
4500 to 5000
5000 to 6000
5500 to 6500
6500 to 7500
7000 to 8000
8000 to 9000
8500 to 9500
9500 to 10500
11000 to 12000
12000 to 13000
13500 to 14500
14500 to 16000
15500 to 17000
18000 to 20000
21000 to 23000
23000 to 25000
25500 to 27500
28000 to 30000
5
Top floor under
insulated roof
(no attic)
4500 to 5000
5500 to 6500
6000 to 7000
7500 to 8500
8500 to 9500
10000 to 11000
11000 to 12000
11500 to 12500
13000 to 14000
15000 to 16000
17000 to 18000
19000 to 20000
21000 to 22000
23000 to 24500
26500 to 28500
30500 to 32500