Suggested starting size
1.25 ton
Arrange a professional heat-load checkHow 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.
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.
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.
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.