AC Size Calculator

An air conditioner that's too small will never keep up with a Houston August. One that's too big cools too fast, shuts off early, and leaves your house cold and clammy because it never runs long enough to pull humidity out. Getting the size right matters.

Enter your details below for a quick estimate of the size you likely need.

How AC sizing works

Air conditioners are measured in tons. One ton equals 12,000 BTU per hour of cooling. It has nothing to do with weight. Most Houston homes land between 2 and 5 tons.

The rule of thumb for our climate is roughly 22 to 25 BTU per square foot, which is higher than cooler parts of the country because our summers are long, hot, and humid. From there you adjust for ceiling height, sun exposure, and how many people live there.

Why bigger is not better

Oversizing is the most common mistake we see on replacement jobs. An oversized unit short cycles. It blasts cold air, hits the thermostat setting fast, and shuts off. Because it never runs a full cycle, it never dehumidifies properly. The result is a house that feels cold and damp, higher power bills, and a compressor that wears out early from constant starting and stopping.

Sizing for a Houston home specifically

National calculators use a milder climate baseline, which is part of why they tend to undersize for us. Houston runs roughly 99 days a year above 90 degrees, with humidity the system has to remove as well as heat. Two local factors move the number more than people expect:

• Ceiling height. A Heights bungalow with eleven foot ceilings holds far more air than its floor area suggests. More on what we run into in the Heights.
• How many systems the house should have. A three-story townhome usually should not be running one, which is the root of most top floor never cools complaints. Larger inner-loop homes often run two, as in West University.

We cover Houston and the surrounding metro. See all service areas, or the full list of HVAC services we handle.

Signs your current system is the wrong size

• It runs constantly on hot days and still can't reach the thermostat setting, likely undersized.
• It cools quickly but the air feels damp and sticky, likely oversized.
• Big temperature swings between rooms.
• The unit turns on and off every few minutes.

If the system is simply not cooling rather than badly sized, start with AC repair, or read why your AC is not cooling. If it is older and facing a large repair, here is how to decide between repair and replacement. No cooling right now? We answer 24 hours a day.