HVAC Load Calculation with HVAC Calculator

Get your HVAC load calculation correct the 1st time with the industries most precise HVAC load calculator. This HVAC Load Calculation Tool provides good faith estimates for general information purposes only.

HVAC Calculator

100 Space Area (SQFT)

8 Space Height (FT)




Calculated Cooling Load: 0 BTU

Many factors may impact or falsify the results of this calculation tool and the accuracy of these results are not guaranteed. Based on a 72F degree indoor, and 95F degree outdoor temperatures, this HVAC load calculation tool utilizes the square foot method to generate an approximation. A full Manual J assessment should be performed by a licensed design engineer for precise measurements

HVAC Calculator

HVAC load calculation with our free easy-to-use HVAC load calculator allows you to quickly and correctly determine the amount of heating and cooling a residential building needs. HVAC load calculations can be tricky, which is why are HVAC calculator formula is based on the buildings specs and design.

Our intuitively designed HVAC load calculator for HVAC companies will help you figure out the recommended equipment capacity for any room or house that you will be working on.

With precise BTU load calculation using our calculator, is shows you the amount of BTUs a certain space requires for sufficient heating and cooling. Using an HVAC BTU formula, it identifies the square footage of the room to determine the capacity—BTUs per hour—needed to reach the desired indoor temperature.

How To Calculate HVAC Load (BTUs)

The proper method for sizing and calculating HVAC load is using The Manual J calculation, which was a technique designed by the Air Conditioning Contractors of America (ACCA). This HVAC load calculation formula is commonly performed with complex computer programs, which require a lot of time and money.

For this reason, ACCA created the BTU load calculator (Manual J) as a rule of thumb. That way, HVAC technicians can determine a general estimate while in the field.

An accurately sized HVAC unit will ensure that the desired space can reach the right temperature without wasting energy. This is how you find that perfect number.

Step One:

Determine the square footage of the home. You can either find this in the home's blueprint or measure out the space room-by-room. Start by taking the length and width of each room and multiplying those measurements to calculate the square footage of that room. Add up the square footage of each room—and there you have it!

Another way to do this is by taking exterior measurements of the entire house and subtracting the square footage of any part of the home not intended to be cooled or heated—like a basement or garage.

Make sure to account for the height of the room, as well. Rooms with tall ceilings tend to demand more BTUs than one with a standard height.

Step Two:

Account for factors that affect insulation. Check to see what grade of insulation the home was built with. If you are unsure, U.S. Standard Insulation is probably your best bet. Other key factors that need to be taken into consideration are sun exposure, windows, and airtightness for the entire home.

Another way to do this is by taking exterior measurements of the entire house and subtracting the square footage of any part of the home not intended to be cooled or heated—like a basement or garage.

Common factors to be accounted for include:

  • Each person living in a home = 100 additional BTUs
  • Each window in a home = 1,000 additional  BTUs
  • Each exterior door in a home = 1,000 additional BTUs

Step Three:

Think about how the living space is being used. Does this home or particular room have heat-producing appliances? How many people regularly occupy the space you are calculating? This should also inform the HVAC load that will be sufficient to heat or cool the intended area.

HVAC Load Calculation Example

To calculate the estimated HVAC load for a house with 2,500 square feet, 12 windows, and 3 exterior doors occupied by 4 people, simply plug it into this formula:

  • 2,500 x 25 = 62,500 base BTU
  • 4 people x 400 = 1,600
  • 12 windows x 1,000 = 12,000
  • 3 exterior doors x 1,000 = 3,000
  • 62,500 + 1,600 + 12,000 + 3,000 = 79,100 BTU

Disclaimer Statement

*The recommended equipment capacities are estimated in good faith and are solely meant for generic, informative purposes. We do not guarantee the accuracy of this information. Please note that other external factors may affect or falsify the recommended BTUs. For accurate values, consult a licensed engineer.

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