HVAC Load Calculator
Calculate BTU Requirements Instantly with our HVAC Load Calculator.
Quickly determine the right heating and cooling capacity for any space and ensure maximum efficiency.
Save time, boost energy savings, and confidently recommend the best HVAC system for your customers. Try our fast, accurate HVAC load calculator today!
Disclaimer:
The outputs, any associated images or diagrams, any measurements, and any and all other information (collectively, the “Outputs”) are provided for informational purposes only and do not constitute a binding quote or professional advice. The Outputs are based on general assumptions and the information you provided, which may not reflect the actual specifications or condition of the subject of the calculation, particularly in the case of complex structures or inputs. Accuracy may also vary depending on location, as some data may be more complete in certain regions than others. Actual results or outcomes may vary significantly following an onsite inspection and detailed assessment by a qualified professional. Any auto-generated visuals are for illustrative purposes and may not accurately represent the subject of the calculation. The Outputs should not be relied upon as a final result or used as the sole basis for financial, renovation, operational, or strategic decisions. Jobber recommends consultation with a qualified professional before proceeding with any work, quotes, or financial decisions. Jobber and its affiliates make no warranties, express or implied, regarding the accuracy, completeness, or suitability of the Outputs, and to the fullest extent permitted by law, we disclaim all liability for any damages or losses arising from reliance on the Outputs.
What is an HVAC load calculator?
Our HVAC load calculator is a free tool that you can use to determine the right size of HVAC unit and the BTU (British Thermal Unit) capacity for any space.
Different factors will increase or decrease heating and cooling requirements. This HVAC sizing calculator makes it easy to plug in those factors and determine the HVAC equipment capacity you’ll need.
When you know the proper sizing for a space’s HVAC system, you can ensure comfortable temperatures and good energy efficiency in any season.
How to calculate HVAC load
Use this HVAC load calculation formula to calculate heating and cooling loads:
| BTU/h = (Square Footage x Ceiling Height) + (Windows x 1,000) + (Exterior Doors x 1,000) + (Occupants x 100) |
Our free heat load calculation for HVAC contractors is designed to use the square footage method. It factors in important values like:
- Square footage is determined by multiplying the length and width of a room. Measure every room, then add up the square footage of every room to get the building’s total square footage. You can also check the building’s blueprints, if you have them handy.
- Ceiling height is easily measured with a tape measure. If ceiling height varies in different rooms, factor that into your calculations—higher ceilings mean more BTUs.
- Windows and doors are opened and closed regularly, and they aren’t always airtight when shut. The more windows and external doors a building has, the more BTUs will be needed.
- The number of occupants will also affect BTU requirements. Determine how many people will regularly use the space. More occupants will mean higher cooling needs.
Examples of HVAC heat load calculation
Want to see how this formula is applied in the field? Let’s explore a couple of examples of commercial and residential heat load calculation.
Example 1
You’re installing an HVAC system in a 3,000-square-foot home for a family of 5. The house has 12 windows, 2 exterior doors, and 8-foot ceilings. Internal loads would look something like this:
- 3,000 x 8 = 24,000 BTUs
- 12 windows x 1,000 = 12,000 BTUs
- 2 exterior doors x 1,000 = 2,000 BTUs
- 5 occupants x 100 = 500 BTUs
According to this residential HVAC load calculation, the correct size of HVAC system is one with a capacity of 38,500 BTUs.
Example 2
In this HVAC load calculation example, you’re calculating capacity for a 15,000-square-foot commercial building with 9-foot ceilings, 30 windows, 6 exterior doors, and 20 occupants:
- 15,000 sq ft x 9-foot ceilings = 135,000 BTUs
- 30 windows x 1,000 = 30,000 BTUs
- 6 doors x 1,000 = 6,000 BTUs
- 20 occupants x 100 = 2,000 BTUs
You will most likely need an HVAC system with 178,000 BTUs to handle this building’s cooling and heating load.
What’s the difference between an HVAC load calculation and a Manual J calculation?
A load calculation is a quick, on-the-go equation that gives you a rough estimate of the HVAC system size you’ll need.
Load calculations are just one component of the more precise Manual J calculation, which is the industry standard calculator developed by the Air Conditioning Contractors of America (ACCA).
In addition to the HVAC load, your Manual J calculation will also account for factors like:
- Different climate regions
- Insulation grade in the building
- Sun exposure for certain rooms
- Other appliances that produce heat
Manual J calculation is the correct way to size an HVAC unit. However, it takes time and software to calculate, which is why many HVAC technicians use load calculation for a quick estimate out in the field.
What are the most common sizes of HVAC equipment?
Residential HVAC units often weigh 1.5–5 tons. Each ton can handle roughly 12,000 BTU/h. Commercial HVAC equipment is much larger at 2–50 tons or even higher.
But it’s important to remember that bigger isn’t necessarily better. The right size of HVAC equipment depends on factors like the building’s square footage, airtightness, and occupancy.
Use our free HVAC load calculator to ensure you’re using the right system size for the space.
Start calculating your HVAC load
Our free tool can help with fast, easy heating and air conditioning load calculation. Estimate your equipment BTUs while you’re on-site, then do your Manual J calculation when you’re finalizing your system design.
Looking for more tools to help you run your HVAC business more effectively? Check out our HVAC parts markup calculator, inspection checklist, and installation checklist.