Find the perfect AC tonnage for your room in seconds with our room size AC calculator. It factors in room area, sunlight, number of people, your city's climate and floor type — so you avoid overpaying for extra capacity or ending up with an AC that can't cool properly. Need help understanding the math? Check our AC Size Calculator Guide .
Our room size calculator for AC starts with the industry-standard 20 BTU per sq ft rule, then adds 600 BTU for each additional person. It applies your sunlight factor (1.0–1.2×), floor correction (+10% for top floors), and a city-specific climate multiplier calibrated for Indian conditions — from cool Himalayan zones to scorching Rajasthan summers.
South and west facing rooms receive direct afternoon sun — the hottest part of the day. This increases the cooling load by 10–20% compared to a north-facing room of the same size. Selecting "High" sunlight in the AC unit size calculator automatically increases your required BTU rating, often pushing the recommendation up one size.
A 5-star BEE-rated AC consumes roughly 30–35% less electricity than a 3-star model of the same tonnage. For 6–8 hours of daily use in Indian summers, this translates to ₹2,000–5,000 in annual savings. The higher upfront cost of a 5-star model is typically recovered within 2–3 seasons. Always check the ISEER rating when buying.