AC Tonnage Calculator
This ac tonnage calculator finds the cooling size a room needs from its area, a load factor, and the number of extra people. Enter them and the ac tonnage calculator returns the cooling load in BTU per hour and the size in tons. It works as an air conditioner tonnage calculator for a single room, so you can estimate ac tonnage before you shop.
Results
The AC Tonnage Calculator is part of our Cooling & Heating collection. Browse more cooling & heating to size, convert, and check your work alongside this tool.
What the ac tonnage calculator shows
One ton of cooling removes 12,000 BTU per hour, and the ac tonnage calculator works out how many tons a room needs. It converts the area to square feet, multiplies by a load factor, adds heat from extra people, and divides by 12,000. Whether you call it an air conditioner tonnage calculator, an ac unit tonnage calculator, or an aircon tonnage calculator, it sizes the same cooling load.
How the air conditioner tonnage calculator sizes a unit
The air conditioner tonnage calculator builds the cooling load, then converts it to tons:
The load factor sets the base heat per square foot, each extra person adds about 600 BTU, and 12,000 BTU is one ton. This is the ac tonnage calculation formula behind the tool, and it is why a bigger or sunnier room lands on a larger size.
Air conditioner ton calculator example
A 50 m² room at 20 BTU per square foot with 2 extra people. The air conditioner ton calculator applies the formula:
So the room needs about a 1 ton unit. Change the area and the ac tonnage calculator returns a new size at once.
How to use the ac tonnage calculator
Enter the room area, a load factor in BTU per square foot, and the number of extra occupants, then the ac tonnage calculator returns the cooling load and the size in tons. Use about 20 BTU per square foot for an average room, more for a sunny or poorly insulated one. This air conditioner ton calculator gives a starting size; a full room by room survey refines it.
Reading the ac tonnage calculator result
The BTU per hour is the cooling load; the tons is the unit size that meets it. Round to the nearest standard size, since units come in half ton steps. Do not oversize on purpose: a unit that is too large short cycles, cools fast without pulling moisture, and leaves the room clammy. If the result sits between sizes, tighten the inputs or run a fuller survey rather than jumping up. The ac tonnage calculator gives a sound starting point for a single room.
When to estimate ac tonnage
- Sizing a room unit when you estimate ac tonnage before buying
- Checking a quote where you determine ac tonnage yourself
- Figuring ac tonnage for an addition or converted space
- Comparing rooms with an hvac tonnage calculator
Common ac tonnage calculator mistakes
- Oversizing on purpose. A unit past the load short cycles and leaves the room humid, so determine ac tonnage from the load, not a guess.
- One factor for every room. Sunny and shaded rooms need different load factors when you estimate ac tonnage.
- Copying the old size. Many old units were too big, so figure the load fresh rather than matching the nameplate.
Tips for right-sizing
- Use about 20 BTU per square foot and adjust for sun and insulation.
- Round to the nearest half ton, not far above the load.
- Run a fuller survey for a whole house rather than one block figure.
- For an installed unit, find the tonnage from the model number on the outdoor condenser.
How to calculate ac tonnage by room size
To calculate ac tonnage by room size, start with area and a load factor, since most of the heat scales with floor space. Twenty BTU per square foot suits an average insulated room; a sunny west facing room or one with big windows runs higher, and a shaded, well sealed room runs lower. Add roughly 600 BTU for each person beyond the first two, and more for a kitchen or a room full of gear. The ac ton calculation for room size then divides the total by 12,000 to reach tons. This is a block load method, quick and good for one room; for a whole house, a full survey folds walls, windows, and infiltration into the total for a tighter figure, and the furnace size calculator sizes the heating side of the same room.
How to find ac tonnage on an existing unit
When you replace a unit rather than size a new room, how to find ac tonnage shifts to reading a label. The model number on the condenser almost always encodes the capacity: look for 18, 24, 30, 36, 48, or 60, which map to 1.5, 2, 2.5, 3, 4, and 5 tons at 12,000 BTU each. The metal nameplate also lists BTU or tons directly. Do not assume the old size was right, though, since many older units were oversized; run the room through this air conditioner tonnage calculator and compare before you match the old capacity.
Ac tonnage calculator per square foot chart
Rough cooling size by room area at 20 BTU per square foot, a quick check on the ac tonnage calculator per square foot result:
| Room area | Cooling load | AC size |
|---|---|---|
| 25 m² | 5,400 BTU/h | 0.5 ton |
| 50 m² | 10,800 BTU/h | 1 ton |
| 75 m² | 16,150 BTU/h | 1.5 tons |
| 100 m² | 21,500 BTU/h | 2 tons |
AC Tonnage Calculator FAQ
How do you calculate ac tonnage?
Convert the area to square feet, multiply by a load factor near 20 BTU per square foot, add about 600 BTU per extra person, then divide by 12,000. That is how to calculate ac tonnage, and what this tool does.
How do I find the tonnage of an existing ac unit?
Read the model number on the outdoor unit. A number like 24 or 36 in it usually means 24,000 or 36,000 BTU, which is 2 or 3 tons. That is how to find ac tonnage on a unit already installed.
What is air conditioner tonnage per square foot?
A rule of thumb near 20 BTU per square foot, or about one ton per 55 to 60 m². The air conditioner tonnage per square foot rule is a starting point, not a substitute for a survey.
Is a bigger unit better?
No. An oversized unit short cycles, cools without removing humidity, and wastes energy. Size to the load rather than rounding far up.