Room size
Room size
One closed room. A 10×15 bedroom is 150 sq ft — the 5,000 BTU band on the chart.
Measure the floor you want cooled, not the whole house.
Sun
Heavy shade −10%. Very sunny +10%. Mixed leaves the chart alone.
Room type
A kitchen adds 4,000 BTU on the ENERGY STAR-style adder. Stoves dump heat the chart otherwise ignores.
Recommended size
- Room
- —
- Chart BTU
- —
- Typical range
- —
- Window units
- —
Enter a room size.
This is a chart estimate for a window or portable room unit. It is not an HVAC load calculation, not a Manual J, and not a whole-house HVAC recommendation. It will not pick central air, a heat pump, or a furnace. Ceiling height, insulation, occupancy, and climate are outside this square-foot table. Confirm the nameplate BTU on the unit you buy.
Room chart, not house tons
A window air conditioner is sold in BTU per hour for one room. The number on the box is not a whole-house “tonnage,” and this page will not pretend it is. Square-foot bands follow an ENERGY STAR-style room air conditioner chart (approximate, about an 8-foot ceiling). After the lookup: −10% for heavy shade, +10% for a very sunny room, +4,000 BTU if it is a kitchen. Then round down to the nearest thousand and map onto typical window/portable sizes: 5k, 6k, 8k, 10k, 12k, 14k, 18k. Chart rows that land on 7k or 9k become the two neighboring shelf sizes. That is still not a Manual J and not a whole-house HVAC size.
sqft = L × W (or enter square feet)
chart_BTU = ENERGY STAR-style room band (approx.)
adjusted = chart_BTU × sun_factor + kitchen? 4000 : 0
shade 0.9 · mixed 1.0 · sun 1.1
look_for = floor(adjusted / 1000) × 1000
shelf_size = nearest typical window units
5k, 6k, 8k, 10k, 12k, 14k, 18k
Example: 10×15 ft = 150 sq ft → chart 5,000 BTU (5k unit). 20×20 ft = 400 sq ft → chart 9,000 BTU, typical window units 8k or 10k. A kitchen on that 150 sq ft room adds 4,000 and lands on the same 8k/10k shelf band.
FAQ
How does the room square-foot chart pick a BTU number?
The page looks up the floor area of one closed room on an ENERGY STAR-style room air conditioner chart (approximate, about an 8-foot ceiling). 10×15 ft is 150 sq ft and lands in the 5,000 BTU band. 20×20 ft is 400 sq ft and lands in a higher band — 9,000 BTU on the chart. Enter length × width or square feet; the whole house is not the input. This is a room table, not a Manual J and not a whole-house HVAC size.
Why typical window units of 5k, 6k, 8k, 10k, 12k, 14k, and 18k?
Those are the window and portable sizes people actually buy. Chart rows that land on 7,000 or 9,000 BTU are not common shelf SKUs, so this page names the two neighboring sizes: 7k becomes 6k or 8k, 9k becomes 8k or 10k. 18k is the largest typical single unit this page will name. A 2-ton central system is a different product — this page will not convert a room chart into house tonnage.
How do shade, sun, and a kitchen change the number?
After the square-foot lookup: heavy shade multiplies by 0.9 (−10%), a very sunny room multiplies by 1.1 (+10%), mixed sun leaves the chart alone. A kitchen then adds 4,000 BTU because a stove dumps heat the floor-area table otherwise ignores. Fixture: 150 sq ft mixed, kitchen → 5,000 + 4,000 = 9,000 BTU, which maps to 8k or 10k on the shelf. These are ENERGY STAR-style adders on a room chart, not a climate or insulation model, and not a Manual J.
Is this a Manual J load calculation?
No. Manual J is a whole-house HVAC load calculation — insulation, windows, occupancy, climate, ductwork, and the rest of the envelope. This page is a square-foot room chart for a window or portable unit. Ceiling height, insulation, occupancy, and climate are outside this table. Confirm the nameplate BTU on the unit you buy. Chart estimate only — not whole-house HVAC.
Can I use this to size whole-house HVAC?
No. Not whole-house HVAC. Not central air, not a heat pump, not a furnace, not house tonnage. One closed room, window or portable. If the chart goes past 18,000 BTU, the chart-level answer is a second room unit — still not a central system. A house in tons is a different job.
Do I size a portable AC the same way?
For a single room, yes — same floor-area chart, same shade/sun/kitchen adders, same 5k–18k shelf list. A portable still needs a window kit to dump heat outside. This page does not size mini-splits or central systems. Chart estimate only — not a Manual J, not whole-house HVAC.