Room Air Conditioner BTU & Cooling Calculator
Calculate room air conditioning BTU capacity, tonnage, and kilowatt cooling requirements adjusted for sunlight, ceiling height, and occupancy.
Room Specifications
HVAC Sizing Specifications
Standard Room AC Sizing Chart
About this tool
How to use it
- Select your measurement unit system (US Customary in feet/sq ft or Metric in meters/m²).
- Enter the room length, width, and ceiling height (default 8 ft / 2.44 m).
- Select your room exposure (sunny, shaded, or normal), number of occupants, and room type (e.g. kitchen).
- Specify your home insulation quality and climate zone, then click Calculate Cooling Capacity to review exact BTU/hr, cooling tonnage, and kilowatt cooling requirements.
Why it matters
Buying an undersized air conditioner leaves your room uncomfortably hot and runs the compressor continuously, while an oversized unit cools too quickly without dehumidifying, creating a clammy, mold-prone environment. This calculator implements official ENERGY STAR and AHAM (Association of Home Appliance Manufacturers) thermal load formulas to specify the ideal cooling capacity.
When to use it
Use this calculator before buying a window air conditioner, portable AC unit, or ductless mini-split system, when finishing a basement or attic renovation, or when verifying HVAC contractor equipment quotes.
Good to know
Calculations follow standard AHAM baseline cooling tables with ENERGY STAR environmental modifiers (+10% for sunny rooms, -10% for shaded rooms, +600 BTU per person above 2 occupants, and +4,000 BTU for kitchens).
Common questions
What happens if you buy an air conditioner that has too many BTUs?
An oversized air conditioner cools the room too quickly before running long enough to remove ambient moisture from the air. This short-cycling leads to high indoor humidity, a cold clammy feeling, premature compressor wear, and higher electric bills.
How many BTUs per square foot are needed for cooling?
A standard rule of thumb is approximately 20 to 25 BTUs per square foot of living space for rooms with 8-foot ceilings. However, adjustments must be made for sunlight exposure (+10%), poor insulation (+15%), additional occupants (+600 BTU each), high ceilings, and kitchens (+4,000 BTU).
How many BTUs are in 1 Ton of air conditioning?
One ton of refrigeration equals 12,000 BTU/hour (approximately 3.517 kW of cooling power). A 24,000 BTU unit is 2 Tons, while a standard 6,000 BTU bedroom window unit is 0.5 Tons.
What electrical outlet circuit is required for a room air conditioner?
Units up to 12,000 BTU typically run on standard residential 115-volt / 15-amp electrical circuits. Larger units (14,000 to 24,000 BTU) usually require a dedicated 230-volt / 20-amp or 30-amp circuit with specialized NEMA receptacle plugs.
What is the difference between SACC and ASHRAE BTU ratings on portable ACs?
ASHRAE is the older gross cooling capacity test rating, while SACC (Seasonally Adjusted Cooling Capacity) is the newer, stricter Department of Energy standard that accounts for heat radiated from exhaust hoses and room air infiltration. A portable AC rated at 12,000 BTU ASHRAE typically delivers around 8,000 to 9,000 BTU SACC.