BTU Chart for Room Size

This is the BTU chart for room size in its standard form: the widely published, Energy Star-style guidance that matches a room’s floor area to the air conditioner size it needs. Find your room’s area in the left column and read across for the size to buy. The chart comes with assumptions, and they matter, so they are spelled out plainly below it — along with a metric version, the tonnage equivalents, and what changes in open-plan and multi-room homes. If your room is not standard, our AC BTU calculator applies the adjustments for you.

The BTU chart for room size (square feet)

Room area (sq ft)	Recommended size (BTU)
100–150	5,000
150–250	6,000
250–300	7,000
300–350	8,000
350–400	9,000
400–450	10,000
450–550	12,000
550–700	14,000
700–850	18,000
850–1,000	18,000
1,000–1,200	21,000
1,200–1,400	23,000
1,400–1,500	24,000
1,500–2,000	30,000
2,000–2,500	34,000

To use it, measure the room’s length and width in feet and multiply them together. A 12 by 14 foot bedroom is 168 square feet, which lands in the 150–250 row, so a 6,000 BTU unit is the starting point. If your adjusted figure falls between two standard sizes, the usual advice is to take the nearer one — and to read the sizing logic behind the chart in our guide to what size air conditioner you need, which works through the adjustments with an example.

What this chart assumes

Every figure in the chart rests on the same set of assumptions, and it is better to state them plainly than to hide them: ceilings of 8 feet, average insulation, moderate sun exposure, and two occupants in the room. If your room departs from that picture, adjust the chart figure before you buy:

• Very sunny room: add 10%.
• A kitchen: add 4,000 BTU for cooking heat.
• Extra people: add 600 BTU for each regular occupant beyond the first two.
• Taller ceilings: scale up roughly in proportion to the extra volume above 8 feet.

One honesty note applies to this chart and to every rule of thumb like it: they are starting points, not engineering. A chart cannot see your insulation, your windows or your climate. For whole-home systems, a proper ACCA Manual J load calculation is the professional standard, and it replaces charts and rules of thumb entirely.

The metric chart: square meters and kilowatts

Outside North America, rooms are measured in square meters and units are sold by kilowatts. The figures below are converted approximations, rounded to the nominal sizes that metric units are actually sold in, so treat them as equivalents rather than exact conversions.

Room area (m²)	Unit size (kW)	Approximate BTU
10	1.5 kW	5,000
15	1.8 kW	6,000
25	2.1 kW	7,000
30	2.3 kW	8,000
37	2.9 kW	10,000
46	3.5 kW	12,000
65	4.1–5.3 kW	14,000–18,000
93	5.3–6.2 kW	18,000–21,000

Tonnage equivalents: when BTU become tons

Central air conditioners are quoted in tons instead of BTU. One ton of cooling equals 12,000 BTU per hour — a leftover from the days when cooling was measured against the ice a system could melt in a day. The common equivalents are:

• 12,000 BTU = 1 ton
• 18,000 BTU = 1.5 ton
• 24,000 BTU = 2 ton
• 30,000 BTU = 2.5 ton
• 36,000 BTU = 3 ton

The two languages exist because the equipment serves different scales. A whole home needs tens of thousands of BTU, so tons are a convenient shorthand — saying “3 ton” is easier than saying “36,000 BTU.” A single room needs far less, and the differences between room units are small, so BTU give the finer steps that room shopping needs: the gap between a 5,000 and a 6,000 BTU bedroom unit matters, and it would be an awkward fraction of a ton.

Open-plan spaces and multi-room homes

The chart works best where the air can actually reach. In one big open-plan space, that is straightforward: treat the whole area as one room, size a single unit (or a planned pair) to the total square footage, and place it so the cool air can circulate across the space. Open-plan living and kitchen areas are exactly where the kitchen adjustment matters most, because the cooking heat and the sitting area share the same air.

Separate, walled rooms are a different story. Each closed room needs its own capacity reaching it, because cool air does not pass through walls or closed doors. A single powerful unit in a hallway will leave the hallway cold and the closed bedrooms warm — the most common disappointment behind “my AC is big enough but the bedrooms are hot.” The honest fixes are per-room units sized from the chart room by room, or a ducted or multi-split system designed for the home, where each room gets its own outlet or indoor head.

Whichever layout you have, start with the area, then apply the adjustments, then check the result against the chart. If you would rather have the arithmetic done for you, run your room through the AC BTU calculator and compare the figure it returns with the chart row for your area — they should tell the same story.

Frequently asked questions