Free Houston Tool
Houston AC Tonnage & Sizing Estimator
Sizing an air conditioner in Houston is not the same as sizing one in a dry climate — our humidity and 9-month cooling season punish both undersized and oversized systems. This free estimator gives you a starting tonnage from your square footage, ceiling height, and sun/insulation profile so you can sanity-check a contractor's quote before you sign.
Living space you want cooled (400–10,000 sq ft).
Recommended nominal size
Estimated cooling load
This is a planning estimate only — actual requirements depend on an on-site assessment by a licensed Houston pro. Houston's humidity and long cooling season make an oversized unit a common, costly mistake — it short-cycles and never dehumidifies. A licensed contractor confirms sizing with a full Manual J calculation.
How AC sizing works in Houston
The estimate starts from a base cooling load of roughly 30 BTU per square foot, then adjusts for ceiling height (taller rooms hold more air to cool) and sun/insulation (a sun-drenched or pre-1995 home leaks heat). The adjusted BTU load is divided by 12,000 (one ton = 12,000 BTU/hr) and rounded up to the nearest standard unit size.
Why right-sizing matters here
An oversized unit is the most common — and most expensive — Houston mistake. It cools the air fast but shuts off before pulling out humidity, leaving your home cold and clammy and cycling the compressor to an early death. A properly sized system runs longer, dehumidifies, and lasts. Always confirm with a Manual J load calculation before buying.
Frequently asked questions
How many square feet does a 3-ton AC cool in Houston?
As a rough Houston rule, a 3-ton (36,000 BTU) system covers roughly 1,400–1,800 sq ft depending on ceiling height, insulation, and sun exposure — less than the national estimate because our cooling loads run higher. Use the estimator above for your specific home, and confirm with a Manual J calculation.
Is it better to oversize an AC in Houston's heat?
No. Oversizing is the single most common Houston HVAC error. A too-large unit short-cycles, never runs long enough to remove humidity, and wears out its compressor early. Correct sizing — not maximum sizing — gives the best comfort and lifespan in our humid climate.
What is a Manual J load calculation?
Manual J is the ACCA industry-standard method for calculating a home's exact heating and cooling load, accounting for insulation, windows, orientation, air leakage, and local design temperatures. A reputable Houston contractor runs one before recommending equipment; this estimator is a quick approximation of the result.
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