Sixteen hundred square feet is a three-bedroom house, the main level of a split-level, or the upstairs of a two-story. The load is 32,000 BTU/hr, 2.67 tons, which rounds up to 36,000 BTU: a 3-ton system. It is a comfortable 3-ton fit, with 4,000 BTU of margin in an average house.
That margin covers strong sun (35,200), four people (33,200) and a kitchen (36,000 exactly). Poor insulation (36,800), a 10 ft ceiling (40,000), a hot sunny exposure (38,700) or sunny with poor insulation (40,500) need 3.5 tons, which the calculator shows as the next size it knows, 48,000 BTU; read that as 3.5, not 4. Shade alone (28,800) or shade with good insulation (25,900) bring a 1,600 sq ft house down to 2.5 tons.
If this is the upstairs of a two-story house, use the poor insulation row unless the attic is insulated to R-49 or better. The second floor sits under the roof deck, takes the heat from the first floor rising through the stairwell, and consistently runs warmer than the rule predicts. Two-story homes with 1,600 sq ft per floor almost always use two systems, one per floor, and the upstairs one is often the larger of the two despite identical footage.
Ceiling height is the factor people forget at this size. Sixteen hundred square feet with 9 ft ceilings is 36,000 BTU/hr before anything else, and with 10 ft ceilings it is 40,000. A great room with a vaulted ceiling should be measured to the average height, not the wall height. Half a ton of AC hides in the ceiling of a lot of 1,600 sq ft homes.
Heating 1,600 sq ft runs 48,000 BTU/hr in a hot climate, 64,000 in a moderate one (18.8 kW) and 88,000 in a cold one (25.8 kW). A 60,000 BTU furnace is slightly under in a moderate climate once you account for output versus input, so 80,000 is the common install; the cold case wants 100,000, or 80,000 with good insulation (74,800). A 3-ton cold-climate heat pump with backup strips is the electric alternative.
Example: a 1,600 sq ft single-story with 9 ft ceilings, a kitchen, four people, average sun and insulation, moderate climate. 1,600 × 20 = 32,000, times 1.125 for the ceiling is 36,000, plus 1,200 for the people and 4,000 for the kitchen, is 41,200 BTU/hr, a 3.5-ton system. With 8 ft ceilings, shade and good insulation it is 25,900 + 5,200 = 31,100, and 3 tons has margin.
Cooling BTU for 1,600 sq ft by sun exposure and insulation
Two occupants, 8 ft ceiling, moderate climate. Each cell shows BTU/hr needed and the unit size to buy.
| Sun exposure | Poor insulation | Average insulation | Good insulation |
|---|---|---|---|
| Heavily shaded | 33,100buy 36,000 BTU | 28,800buy 30,000 BTU | 25,900buy 30,000 BTU |
| Average | 36,800buy 48,000 BTU | 32,000buy 36,000 BTU | 28,800buy 30,000 BTU |
| Very sunny | 40,500buy 48,000 BTU | 35,200buy 36,000 BTU | 31,700buy 36,000 BTU |
Common adjustments for a 1,600 sq ft room
| Scenario | Cooling BTU/hr | Unit to buy |
|---|---|---|
| Average (baseline) | 32,000 | 36,000 BTU |
| 4 people instead of 2 | 33,200 | 36,000 BTU |
| 10 ft ceiling | 40,000 | 48,000 BTU |
| Kitchen in the space | 36,000 | 36,000 BTU |
| Hot climate, very sunny | 38,700 | 48,000 BTU |
Heating BTU for 1,600 sq ft by climate and insulation
| Climate | Poor insulation | Average insulation | Good insulation |
|---|---|---|---|
| hot | 57,60016.9 kW | 48,00014.1 kW | 40,80012.0 kW |
| moderate | 76,80022.5 kW | 64,00018.8 kW | 54,40015.9 kW |
| cold | 105,60030.9 kW | 88,00025.8 kW | 74,80021.9 kW |
1,600 sq ft sizing questions
What size air conditioner do I need for a 1,600 sq ft room?
About 32,000 BTU/hr in average conditions (2.7 tons), so a 36,000 BTU unit. The table above covers sunnier and worse-insulated rooms.
Is 3 tons enough for 1,600 sq ft?
Yes for an average house: the load is 32,000 BTU/hr and 3 tons is 36,000. Poor insulation (36,800), a 10 ft ceiling (40,000) or a sunny, poorly insulated exposure (40,500) push it to 3.5 tons. A shaded house (28,800) fits 2.5 tons.
How do I size AC for the upstairs of a 1,600 sq ft two-story?
Use the poor insulation row unless the attic is at R-49 or better, because the second floor sits under the roof and collects heat rising from below. That puts a 1,600 sq ft upstairs at about 36,800 BTU/hr, or 3.5 tons, rather than the 3 tons the footage alone suggests.
What size furnace for 1,600 sq ft?
About 64,000 BTU/hr in a moderate climate with average insulation and 88,000 in a cold one. In practice that is an 80,000 BTU furnace for most of the country and 100,000 in the north, or 80,000 in the north with good insulation.