BTU & AC Size FAQ

What size AC do I need for my room?

Start at 20 BTU per square foot, then add for people, sun and a hot climate or trim for a shaded, well-insulated room. Use the calculator with your real numbers to get a concrete BTU and tonnage.

Is it better to oversize or undersize an AC?

Neither extreme is good. An oversized unit cools too fast, short-cycles, and removes little humidity, leaving the room clammy. An undersized unit runs constantly and never reaches temperature. Aim for the calculated size, rounded to the nearest common unit.

How many square feet does one ton cool?

Roughly 400–600 sq ft per ton (12,000 BTU) under average conditions, but climate, ceiling and insulation move that a lot. In a hot climate plan closer to 400 sq ft per ton.

Does ceiling height change BTU?

Yes. Above an 8 ft standard, cooling load scales with ceiling height: a 10 ft ceiling adds about 25%. The calculator applies ceilingHeight ÷ 8 automatically.

Why does a kitchen need more BTU?

Ovens, stoves and fridges dump heat into the room. The calculator adds a flat 4,000 BTU for a kitchen; a good range hood venting outside helps more than a bigger AC.

Are these calculators professional advice?

No. They use standard HVAC rules of thumb for planning. For a new installation, confirm with a Manual J load calculation done by a licensed technician.