HVAC Load Calculator (BTU)
Calculates heating and cooling load in BTUs for proper system sizing based on square footage and conditions
Total square footage of the space
Height of the ceilings
Regional climate conditions
Quality of existing insulation
Enter area to calculate base BTU load
Select all options to see adjusted load
HVAC tonnage rounded to nearest half ton
Suggested HVAC unit size
Frequently Asked Questions
How many BTUs do I need per square foot?
A general rule of thumb is 20-25 BTUs per square foot for cooling, but this varies significantly by climate, insulation quality, window area, and ceiling height. A well-insulated home in a moderate climate may need only 20 BTUs per square foot, while a poorly insulated home in a hot climate may need 30 or more.
What is a ton of air conditioning?
One ton of air conditioning equals 12,000 BTUs per hour of cooling capacity. A typical residential system ranges from 1.5 to 5 tons. The name comes from the amount of heat needed to melt one ton of ice in 24 hours.
What happens if my HVAC system is too big?
An oversized system cools the air quickly but cycles on and off frequently (short cycling). This wastes energy, increases wear on the equipment, and fails to adequately dehumidify the air. Proper sizing is more efficient and comfortable than oversizing.
Does ceiling height affect HVAC sizing?
Yes. Higher ceilings mean more air volume to heat or cool. Standard 8-foot ceilings are the baseline. A room with 10-foot ceilings has 25% more volume and needs roughly 20% more BTU capacity. Vaulted or cathedral ceilings may need even more adjustment.
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