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HVAC Unit Sizing Calculator

Calculate what size Air Conditioner or Heat Pump you need based on square footage, climate zone, and ceiling heights.

Oversizing an AC unit is a $8,000 mistake. Avoid short-cycling and humidity traps by calculating the precise tonnage your home requires.

Run Your Own Simulation

Adjust the inputs below. Results update instantly. No signup, no data saved — everything runs in your browser.

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Stop Guessing Your Tonnage

Many “old-school” HVAC contractors still use the generic “500 sq ft per ton” rule of thumb. In modern, well-insulated homes, this antiquated math often results in recommending an oversized unit that costs too much and performs poorly.

How to use this calculator

  1. Enter your home’s cooled square footage.
  2. Select your geographic climate zone (Texas requires vastly more BTUs per sqft than Maine).
  3. Adjust your ceiling height (Vaulted 12ft ceilings drastically increase the cubic volume of air that needs cooling).
  4. Honestly assess your insulation.

Why Tonnage Matters

A 3.0 Ton unit removes 36,000 BTUs of heat per hour. If your home only requires 24,000 BTUs, buying the 3.0 Ton unit means it will blast freezing air, turn off in 5 minutes, and leave your house feeling muggy. Dehumidification requires steady, prolonged airflow.

Frequently Asked Questions

A 'Ton' of air conditioning refers to the cooling capacity. One ton equals 12,000 British Thermal Units (BTUs) of heat removal per hour.
No! An oversized unit will cool the house too fast and shut off before it has a chance to dehumidify the air. This leads to a clammy, mold-prone environment and burns out the compressor through 'short-cycling'.

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