Your result
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Enter your values, then click Calculate result.How this calculator helps
Get a preliminary cooling-capacity estimate before comparing air conditioners. Room area is adjusted for ceiling height, then converted into approximate BTU per hour and common tonnage sizes using a configurable heat-load factor.
How to use it
- 1
Measure the room's internal floor area and note the ceiling height.
- 2
Choose a heat-load factor suited to a warm climate and normal residential use.
- 3
Discuss sun exposure, windows, insulation and occupancy with a qualified installer before purchase.
Formula and methodology
Estimated BTU/h = room area × ceiling-height adjustment × heat-load factor. One refrigeration ton is approximately 12,000 BTU/h.
Uses measured dimensions and editable local rates for preliminary planning. It is not a bill of quantities, structural design or valuation.
Worked calculation example
A 180 sq ft room with a 10 ft ceiling and a 65 BTU-per-square-foot planning factor needs roughly 13,000 BTU/h, suggesting the next practical size near 1.25 tons.
How to interpret your result
Treat tonnage as a screening estimate; insulation, sun exposure, occupants and equipment require a proper heat-load assessment.
Input guide
Measure conditioned floor area and ceiling height.
Increase the heat factor for strong sun, poor insulation or large glazing.
Account for occupants and heat-producing equipment.
Scenario comparison
| Scenario | What it demonstrates |
|---|---|
| 120 sq ft shaded bedroom | often needs less capacity than the same area in direct sun. |
| 180 sq ft room with 10 ft ceiling | tests a common residential case. |
| Top-floor west-facing room | requires a higher heat-load allowance. |
Common mistakes to avoid
- Choosing capacity by floor area alone.
- Oversizing and causing short cycling or poor humidity control.
- Ignoring insulation, windows and outdoor design temperature.
Have a qualified HVAC installer calculate the room heat gain before purchase.
What can affect the result?
Solar heat
West-facing windows and an exposed roof can add substantial afternoon heat.
People and equipment
Occupants, computers, cooking and lighting add heat to the room.
Insulation and leakage
Poor roof insulation and gaps around doors increase the required cooling capacity.
Limits of this estimate
Area-based sizing is only a first estimate; it cannot replace a room-by-room heat-load calculation or confirm electrical and installation requirements.
Sources and review information
Frequently asked questions
Is the AC tonnage estimator free?＋
Yes. SolvePilot tools are free, work in your browser, and require no account.
Does SolvePilot store my values?＋
No. Calculations run locally in your browser and the values you enter are not sent to a server.
Should I treat the result as an exact bill or quotation?＋
No. Results are informed estimates. Final charges can vary because of taxes, tariffs, lender terms, usage patterns, or provider rules.
How can I improve the accuracy?＋
Use recent values from your own bill, statement or institution, review every assumption, and confirm important results with the relevant official source.
Should a sunny top-floor room use more capacity?＋
Usually yes. Direct sun, roof heat, large windows, occupants and appliances increase the cooling load.