Worked example: BTU Calculator
300 square feet. This fixed reference example shows one complete scenario; the interactive results above use your current inputs.
View the example inputs
- Room floor area
- 300 ft²
- Sun exposure
- Average
- Usual occupants
- 2
- Kitchen
- No
| Calculated quantity | Example result |
|---|---|
| Estimated cooling capacity | 8,000 BTU/h |
| Estimated thermal cooling capacity | 2.34 kW |
Understanding a weather index and its valid range
An index describes a particular model
Air temperature, humidity and wind can combine into different reference measures. Wind chill, heat index and dew point do not represent the same physical question. A formula valid for cold, windy conditions should not be extended to warm air, and a shaded heat estimate does not describe every exposure.
Check temperature units, wind units and humidity percentages before interpreting a result. Values at a model boundary can require a different equation or a rejection message rather than a simple continuation of the curve.
Interpret the conditions alongside the number
Direct sun, clothing, exertion, indoor conditions and individual physiology can change actual comfort and risk. A calculated weather index is not an individual exposure limit. A room-cooling chart is likewise a sizing estimate under stated building assumptions.
The linked source and formula identify the reference method. Use current local observations or an entered scenario as inputs; the calculator does not supply a live forecast.
Formula and calculation method
Uses the ENERGY STAR room AC chart for 100–2000 ft² with 8-foot ceilings. At a shared boundary, uses the larger interval conservatively, except the final upper limit.
Adjusts capacity −10% for heavy shade, +10% for strong sun, +600 BTU/h for each occupant above two and +4000 BTU/h for a kitchen.
Scope and Limitations
- Room-unit sizing estimate, not a building heat-load calculation. Climate, windows, insulation and air leakage require assessment.
Reference Sources
Frequently asked questions
How does this calculator work?
Uses the ENERGY STAR room AC chart for 100–2000 ft² with 8-foot ceilings. At a shared boundary, uses the larger interval conservatively, except the final upper limit.
What assumptions should I check?
Room-unit sizing estimate, not a building heat-load calculation. Climate, windows, insulation and air leakage require assessment. Adjusts capacity −10% for heavy shade, +10% for strong sun, +600 BTU/h for each occupant above two and +4000 BTU/h for a kitchen.
Can I save or print this calculation?
Use Copy link with inputs to reproduce the scenario, Download results for a text record, or Print. Where a schedule is shown, its CSV download includes every row.