AC Tonnage Calculator — Air Conditioner Size for Any Room
Find the right AC size in tons and BTU/hr for your room. Enter the floor area, ceiling height, climate zone, number of occupants and sun exposure to get an instant recommendation.
sq ft
ft
Climate zone
Sun exposure
Nearest standard AC size at or above the calculated need
- 1
Base cooling load
25 BTU/ft² × 500 ft² = 12,500 - 2
Ceiling height adjustment
12,500 × ((9 − 8) ÷ 8) × 0.1 = 156 - 3
Total BTU/hr
(12,500 + 156 + 0) × 1 = 12,656Base + ceiling adjustment + occupant load (each person beyond 2 adds 600 BTU/hr), scaled by sun-exposure factor. - 4
Raw tonnage
12,656 ÷ 12,000 = 1.055 - 5
Recommended AC size
Round up 1.055 to nearest standard size = 1.50Snapped up to the next standard AC size: 0.75, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0 or 5.0 tons.
How does this calculator work?
Multiply floor area (sq ft) by a climate BTU/ft² factor, adjust for ceiling height, occupants, and sun, then divide by 12,000 to get tons. Round up to the next standard size. A 500 sq ft warm-climate room with 9 ft ceilings and 2 occupants needs roughly 1.5 tons (≈18,000 BTU/hr).
Formula
How this is calculated
Air conditioner capacity is rated in tons of refrigeration, where 1 ton = 12,000 BTU/hr of heat removal. The basic sizing rule multiplies the floor area by a climate-zone factor (roughly 16–30 BTU/hr per sq ft depending on how hot your region is), then adjusts for ceiling height (rooms taller than 8 ft have more air volume to cool), occupancy (each additional person beyond two generates about 600 BTU/hr of heat), and sun exposure (a south-facing or heavily glazed room gains more solar heat than a shaded one).
The result is then rounded up to the next standard AC size (0.75, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 5.0 tons) so the recommendation matches a real product. Factors not captured here — insulation quality, number and type of windows, heat-generating appliances, and local climate extremes — can shift the true requirement by 10–20%. This calculator gives a reliable starting estimate; a professional Manual J load calculation is recommended for new construction or large commercial spaces.
Climate factors used (2024 estimates, editable via inputs): Hot/Tropical 30 BTU/ft², Warm/Subtropical 25, Moderate/Temperate 20, Cool/Northern 16 BTU/ft².
Frequently asked questions
1 ton of refrigeration equals 12,000 BTU of heat removal per hour — historically the cooling effect of melting one ton of ice over 24 hours. A 1.5-ton AC removes 18,000 BTU/hr and suits rooms of roughly 600–700 sq ft in a warm climate.
No. An oversized AC short-cycles — it cools the air too quickly, switches off before removing enough humidity, and wastes energy. Matching capacity to the actual load gives better comfort, lower bills, and longer equipment life.
The 1 ton = 12,000 BTU/hr definition and the area-based sizing rules are internationally recognised. Input your room area in square feet (1 m² ≈ 10.76 sq ft) and the result translates directly. Many Asian markets express capacity in BTU/hr or kW (1 ton ≈ 3.517 kW).
TG we-Calculate Editorial Team. (2026). AC Tonnage Calculator — Air Conditioner Size for Any Room [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/ac-tonnage-calculator
TG we-Calculate Editorial Team. "AC Tonnage Calculator — Air Conditioner Size for Any Room." TG we-Calculate. 2026. https://we-calculate.com/calculator/ac-tonnage-calculator.
TG we-Calculate Editorial Team, "AC Tonnage Calculator — Air Conditioner Size for Any Room," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/ac-tonnage-calculator
@misc{wecalculate_ac_tonnage_calculator, title = {AC Tonnage Calculator — Air Conditioner Size for Any Room}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/ac-tonnage-calculator}}, year = {2026}, note = {TG we-Calculate} }
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