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AC BTU / Tonnage Calculator
Estimate required BTU/hr and recommended AC tonnage for a room based on dimensions, sun exposure, and occupancy
HVAC
📋ASHRAE rule of thumb (20 BTU/ft²); BEE star rating sizing guide (India)
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Estimation tool only. Results are indicative — not a substitute for professional engineering design or site-specific survey. Always verify with a qualified civil, structural, or MEP engineer before ordering materials or commencing construction.
Calculate
Results are estimates only. Verify with a qualified engineer before use.
Formula
Base BTU = room_area_sqft × 20 BTU/ft² Adjustments: Sun exposure: Low 0%, Medium +10%, High +20% Each additional occupant beyond 2: +600 BTU Kitchen: +4000 BTU 1 Ton AC = 12,000 BTU/hr Recommended tonnage: < 9,000 BTU → 0.75 Ton 9,000–12,000 → 1.0 Ton 12,001–18,000 → 1.5 Ton 18,001–24,000 → 2.0 Ton > 24,000 → 2+ Ton (commercial)
ARoom area (ft²)
20BTU per square foot (ASHRAE rule of thumb)
nNumber of occupants
1 Ton12,000 BTU/hr cooling capacity
Reference Standard
ASHRAE rule of thumb (20 BTU/ft²); BEE star rating sizing guide (India)
Practical Tips
- •Oversizing an AC by more than 25% causes "short cycling" — the unit cools quickly but does not dehumidify, leaving the room clammy.
- •Inverter ACs (variable-speed compressor) save 30–50% on electricity vs fixed-speed; the premium pays back in 2–3 years in India.
- •Ensure the outdoor unit has clear airflow on all sides (min 300 mm clearance) to maintain rated efficiency.