AC Tonnage Calculator

Want to learn how to calculate AC tonnage for your home, office, or commercial space? Whether you're sizing a new system or upgrading an old one, our all-in-one AC tonnage calculator takes the guesswork out of the process.

Our AC sizing tool works just like the best solutions out there — including an AC unit size calculator, HVAC tonnage calculator, and AC tonnage calculator per square foot — to give you precise cooling capacity based on real room data. Just enter your room size, ceiling height, room type, window count, amount of exterior doors, and sunlight exposure, and we’ll show you exactly how many BTU you need, convert BTU to ton, and explain how many tons in a BTU — all using trusted HVAC load calculation and Manual J calculation methods.

Whether you're a homeowner or HVAC pro, this is the ultimate solution for smart, energy-efficient cooling.

When choosing the right air conditioner, tonnage is the most important factor to consider — and knowing how to calculate AC tonnage can save you from poor comfort and high energy bills. In simple terms, tonnage refers to an AC unit's cooling capacity, and it determines how effectively your system will cool a given space.

One ton of refrigeration (TR) equals 12,000 BTU (British thermal units) per hour, or the amount of heat needed to melt a ton of ice in 24 hours. For example, a 2-ton AC unit can remove enough heat to melt 2 tons of ice per day. That's why bigger rooms need more BTUs, and thus more tonnage.

Choosing the wrong tonnage can lead to problems:

• Too little, and your AC will run constantly without fully cooling the space.

• Too much, and it will cool the room too quickly, leaving it cold and damp.

That's why using an AC tonnage calculator — especially one based on AC tonnage per square foot — is so important.

To size your air conditioner correctly, you need to know how to calculate AC tonnage based on your room's specific characteristics — not just guess. That's precisely what our AC tonnage calculator does, using real room data to estimate how many BTU you need, and then converting BTU to ton using standard HVAC load calculation methods.

Here's how it works:

1. Measure your room size. Start by calculating the area of your room:

   area = length × width

   If you don't know it yet, use a measuring tape and enter the dimensions into our AC unit size calculator. The result gives you the base square footage, which is essential for using any AC tonnage calculator per square foot.

2. Account for ceiling height. Standard BTU charts assume 8-foot ceilings. If your room is taller, add 1,000 BTU/hr for each extra foot to ensure proper cooling.

3. Adjust for the number of people. Our calculator assumes 1-2 people in the room. For every additional person, add 600 BTU/hr, as human body heat increases the room's thermal load.

4. Consider room type. If you're cooling a kitchen, add 4,000 BTU/hr to account for heat from appliances. Bedroom? Living room? Each space has different cooling needs — and our calculator takes that into account.

5. Factor in sunlight exposure. A sun-facing room will need about 10% more cooling capacity, while shaded rooms can reduce that requirement by 10%. That's why our AC tonnage calculator asks for window orientation and sun exposure.

6. The result is displayed in TR (ton of refrigeration) — to convert it to BTU/hr, simply multiply by 12,000 BTU per ton:

   1 ton = 12,000 BTU/hr

Need help with the conversions? Check our BTU to tons converter for instant calculations.

Manual J calculation is a standardized method for performing HVAC load calculations, developed by the Air Conditioning Contractors of America (ACCA). The Manual J is the ANSI-recognized national standard for sizing HVAC systems in homes, apartments, townhouses, and small residential buildings, and local building codes across the U.S. often require it.

It determines how much heating or cooling (in BTU) a space truly needs by considering factors like room size, ceiling height, number of people, windows, and exterior doors.

While a basic AC tonnage calculator per square foot can give you a quick estimate, HVAC experts rely on the Manual J calculation.

Here are some standard BTU values used in a Manual J calculation:

1 person = 100 BTU/hr

1 window = 1,000 BTU/hr

1 exterior door = 1,000 BTU/hr

To calculate the total load, you add these values to the base thermal load based on your room’s volume (area × height), or use our cubic feet calculator.

Simplified Manual J calculation formula is as follows:

To better understand how our AC tonnage calculator estimates your cooling requirements, let's analyze two different scenarios based on real-world room setups.

Let’s say you’re using the AC unit size calculator for a small kitchen that measures 200 sq ft, with a ceiling height of 8 ft, 3 people regularly inside, and strong sunlight exposure:

1. Select the calculation method. Choose Quick estimate to get started easily.

2. Input the floor area as 200 square feet.

3. Set the ceiling height to 8 ft.

4. Choose the room type: Kitchen.

5. Mark the Sunlight exposure as a Sunny room.

6. Our AC tonnage calculator will recommend you 0.97 tons. Using the standard BTU per ton ratio, this equals:

   0.97 × 12,000 = 11,660 BTU/hr

Let's refine the first example. The kitchen still measures 200 sq ft with 8 ft ceilings and 3 people, but now it also has 1 exterior door and 2 large windows:

1. Change the calculation method to the Industry-standard Manual J method.
2. Leave the floor area, ceiling height, and number of people.
3. Enter the number of windows: 2.
4. Enter the number of exterior doors: 1.
5. Check the result. You'll need approximately a 0.41-ton AC unit, or 4,900 BTU/hr, for this updated kitchen scenario.