Sizing and calculators
Air conditioner size calculator: Method and Sizing Limits
Convert a known cooling load or a declared area scenario.
Result not yet calculated
Enter the required data. Unknown assumptions do not become guessed values.
Method v1.0. Checked October 14, 2026. Sources and limits.
Paper method and limits
Keep the known output load in BTU/h. Declared area scenario = area times each stated intensity endpoint. Equivalent cooling tons = BTU/h / 12,000. Sensible and latent loads are separately recorded. This does not choose a purchase size.
Sections6
This air conditioner size calculator converts a known whole-house cooling load into BTU/h and tons. It can also show a declared area case when you supply both the heat-rate range and its source. It does not infer a load from floor area alone or round the result into a unit you should buy.
Use a dated design-load report when available. A cooling ton is a heat-rate unit, not a floor-area rule. Divide BTU/h by 12,000 to show equal tons. Keep sensible and latent needs separate. Area mode uses your stated heat-rate and bases without endorsing them. Unknown load remains unknown, and the result is not a matched-unit choice or guaranteed purchase size.
Air conditioner size calculator: central versus room AC
This tool is for central cooling load units. For one room, use the room AC BTU calculator. Its published chart has a different boundary.
ACCA Manual J covers building loads. Manual S covers selecting a matched unit. This tool keeps those tasks separate from unit math.
Known load or declared area scenario
| Mode | Inputs | Result |
|---|---|---|
| Known load | Low/high BTU/h and report source/date | Same load, plus tons conversion |
| Area scenario | ft², your BTU/h/ft² range and assumptions | Area times declared intensity |
| Unknown load | No supported heat-rate basis | No numeric sizing result |
Scroll for more →
Area mode adds no climate multiplier or safety factor. State the building and weather bases yourself. A case does not become a design result because its math is correct.
Air conditioner size calculator: BTU/h and tons
The DOE air-conditioning report defines one refrigeration ton as 12,000 BTU/h. For example, a declared 30,000 BTU/h load converts to 2.5 tons. This is a unit change, not proof that a rated 2.5-ton product meets the design needs.
| Declared cooling load | Equivalent tons |
|---|---|
| 24,000 BTU/h | 2 |
| 36,000 BTU/h | 3 |
| 48,000 BTU/h | 4 |
Scroll for more →
Sensible and latent limits
Sensible cooling removes heat that affects temperature. Latent cooling removes moisture. Total capacity alone does not show how a matched system meets both needs at the stated terms.
Keep the indoor and outdoor full models and their performance data with the report. The tool records optional load splits but does not judge a unit match. No fixed rounding chooses the next larger cabinet.
FAQ
Can floor area alone choose my central AC size?
No. Whole-house loads depend on construction, windows, exposure, leakage and design conditions. The area mode needs your stated heat-rate and source, and is labelled a case. Use a load report and a selection record to choose a unit. The unit conversion does not turn a house-area guess into a checked cooling design for the home.
Is a cooling ton a floor-area measure?
No. It is a heat-rate unit equal to 12,000 BTU/h. Dividing a known load by that constant gives equal tons. A rated product size still needs matched performance and sensible/latent checks at the design conditions. Keep the report and unit records rather than choosing a purchase from the unit conversion alone.
Why does the tool not round up to a unit?
The numeric load and a rated stock size are separate records. Actual unit performance depends on the matched indoor/outdoor set and design conditions. A fixed larger-unit rule could conceal that need. The tool shows the declared load and its equal units. It then directs you to retain the load and choice evidence for the actual bid.
Verdict: use the air conditioner size calculator for declared units
The air conditioner size calculator preserves your load basis and shows the unit conversion clearly. Return to the sizing guide for the right task or the central AC budget tool to price a defined scope.