How to Find AC Tonnage by Model Number

What Tonnage Is My AC Unit? The 60-Second Method

Maybe you're replacing an old unit, comparing quotes from HVAC contractors, or just curious why one room never cools down. Whatever brought you here, you don't need a technician to tell the tonnage of your AC unit. You need about a minute and these four steps:

1. Head outside to the condenser. That's the big metal box with the fan on top, humming away next to your house.
2. Find the data plate. It's a metal or foil sticker on the side panel, usually near the spot where the copper refrigerant lines run into the cabinet.
3. Locate the model number. It's the line marked M/N or Model No. Be careful not to grab the serial number (S/N) sitting right next to it.
4. Spot the capacity code and divide by 12. Somewhere in that string of letters and digits is an even number divisible by 6: 18, 24, 30, 36, 42, 48, or 60. That's your cooling capacity in thousands of BTUs per hour. Divide by 12 and you've got tons.

That's genuinely all there is to it. A model number with 24 in the right spot is a 2 ton unit, 36 is 3 tons, 48 is 4 tons. This works because one ton of cooling equals 12,000 BTU/hr, and manufacturers bake that number straight into their model numbers. The same trick works whether you're trying to determine AC tonnage from a model number on a Carrier, Goodman, Trane, Lennox, Rheem, or York. Pretty much every brand sold in the US plays by this rule.

How to determine AC tonnage from model number, and how to tell tonnage of AC unit from the outside, both come down to reading the model number. How to find tonnage of AC unit for yourself, how to tell how many tons an AC unit is and how to know how many tons is my AC unit use the same steps. How to find the tonnage of an AC unit you did not install yourself, and how to find tonnage on AC unit plates in general, both end at the same plate and the same two or three digits, so the steps above cover all of them.

Where to Find the Tonnage on an AC Unit

Before working out how to tell what ton your AC unit is, it helps to know where to find tonnage on AC unit cabinets at all. People often expect to see "3 TONS" written somewhere on the unit. Sorry, but manufacturers are not that generous. The tonnage on an AC unit is almost never spelled out, because it lives inside the model number on the data plate (some folks call it the nameplate or rating plate). On the outdoor condenser, that plate sits on the side or back panel, typically close to the electrical disconnect and the refrigerant line connections.

One thing that trips people up: the plate lists both a model number and a serial number, usually stacked right on top of each other. The model number (M/N) is the one that contains the size. The serial number (S/N) encodes when the unit was built, not how big it is. If you've been staring at the serial number wondering where the tonnage went, that's why.

If you have a split system, your indoor air handler or furnace coil has its own data plate too, and its model number also carries a capacity code. But for cooling capacity, the outdoor unit's plate is the one to trust. And if you're checking a window or portable AC, you're off the hook entirely, because those print the BTU rating right on the label, so just divide it by 12,000 to get tons.

How to Read the Tonnage Code in a Model Number

Knowing how to read tonnage of AC unit model numbers comes down to one habit: look for a capacity, not a word. So how do you read the tonnage once you're looking at the model number? Manufacturers write capacity in thousands of BTUs per hour, in steps of half a ton (6,000 BTU). That's why the same seven numbers show up across every brand:

Let's decode two real ones so you can see it in action:

Trane 4TTR6036J1000A shows it clearly. The zero-padded 036 after the series letters is the capacity code. 36,000 BTU/hr ÷ 12,000 = a 3 ton unit.

Goodman GSX140361 works the same way. GSX is the product line, 14 is the SEER rating, and 036 is the capacity. Again, 3 tons. Notice how the 14 could fool you if you didn't know it was the efficiency rating. The capacity code is always one of those seven numbers from the chart.

What 024, 030, 036, 042, 048 and 060 Mean

If you already have the three digits and only want the answer, here it is. 018 tonnage is 1.5 tons, 024 tonnage is 2 tons, 030 tonnage is 2.5 tons, 036 tonnage is 3 tons, 042 tonnage is 3.5 tons, 048 tonnage is 4 tons and 060 is 5 tons. The leading zero changes nothing. It is there so that every size takes up three characters in the model number.

Smaller codes exist too, mostly on ductless and room equipment: 009 is 9,000 BTU, or three quarters of a ton, and 012 is 12,000 BTU, exactly 1 ton. Nothing above 060 is a normal home unit. Five tons is the largest single residential size, so a bigger number is either light commercial equipment or not the capacity code.

When Two Numbers in the Model Number Could Both Be the Size

This is where most people get stuck, and it is the commonest question under any video on the subject. A model number can hold a 30 and a 36, or a 24 near the start and a 36 near the end. A few rules settle nearly every case:

• A zero-padded group wins. If the string contains 036 and also a bare 30 somewhere else, the size is 036.
• Take the first padded group after the series letters. Digits that follow the capacity code describe the voltage or the design revision, and they sometimes happen to spell another size.
• Skip the efficiency number. A 13, 14, 15 or 16 sitting just before the capacity code is the SEER rating, which is why it is never one of the seven sizes.
• Ignore the serial number completely. A 24 or a 36 inside the serial is a date or a sequence number.
• Round an odd code to its neighbor. Some units are labeled with the tested capacity, so 035, 047 or 059 mean the 3, 4 and 5 ton sizes.

Tip: when two readings are possible, believe the one that is a standard size and sits in the middle of the model number, then confirm it against the RLA check further down. The decoder lists any second candidate it finds under the main answer, so you can see both.

AC Tonnage Codes by Brand: Quick Reference

Every brand hides the code in a slightly different spot. Here's where to look on the major US brands:

Don't stress about memorizing any of this, because the decoder at the top of this page already knows each brand's format. Pick your brand, paste the model number, done.

Trane Tonnage by Model Number (and American Standard)

Both names use one scheme, so American Standard tonnage by model number reads the same way. Look for a zero-padded three digit group straight after the series characters. In 4TTR6036J1000A the 036 is the size, 3 tons. The trap is a neighboring digit: 4TTB3036E1000AA looks as if it holds a 30 and a 36, but the padded group is 036, so that unit is 3 tons as well. The Trane model number tonnage is always the padded group, never the two digits that happen to sit before it.

Carrier Tonnage by Model Number (and Bryant)

Start by ignoring the first two digits. On these units 24, 25 and 38 name the product family, so Carrier model number tonnage is never at the front. Newer models carry a two digit size near the end: 24ABC636 is 3 tons. For old Carrier tonnage by model number, the 38 series uses a padded three digit group in the middle, so 38BRG060300 is a 5 ton condenser, and the 300 after it is not a size. Carrier condenser tonnage by model number follows whichever of those two patterns the plate shows. Carrier tonnage by serial number does not exist as a reading, because the serial only holds the build date.

Lennox Tonnage by Model Number

Current models set the size off with dashes, which makes Lennox AC tonnage by model number the easiest to read. In ML14XC1-036-230 the middle group is the capacity, 3 tons, and the 230 at the end is the voltage. Much older units used a different code that does not divide by 12, so if the middle group is not one of the standard sizes, use the RLA check further down or ask the manufacturer.

Rheem, York and Goodman Tonnage by Model Number

These three put two or three size digits after the series letters and the efficiency number. Rheem tonnage by model number, and Ruud with it, is the pair after the SEER figure: RA1436AJ1NA is 3 tons. York tonnage by model number is the pair after the four letter prefix: YCJF36S41S1 is 3 tons. Goodman model number tonnage, shared with Amana, is a padded group after the SEER number: GSX140361 is 3 tons, and the 14 before it is the efficiency rating.

Across every brand the rule is the same: skip the family digits and the efficiency number, then read the first group that is a standard size. If your brand is not listed, leave the brand box on its default and the decoder applies that rule for you.

How to Find AC Tonnage Without a Model Number

Labels fade. A unit that's been baking in the sun for 15 years might have a data plate you can barely read. If the model number is gone, here's how to find your AC tonnage without it, in the order I'd try:

1. Check the RLA on the data plate

Even on faded plates, the electrical ratings often survive because they're stamped for code compliance. Find RLA(Rated Load Amps) for the compressor. As a rough rule of thumb, residential compressors draw about 5 to 7 amps per ton at 240V. So an RLA around 16–19 usually points to a 3 ton unit. It's a ballpark, not gospel, but it narrows things down fast.

2. Use the serial number to ask the manufacturer

Here's the thing about serial numbers: you can't determine AC tonnage from a serial number by reading it yourself, because it encodes the manufacture date and factory, not the size. But the manufacturer can. Call the brand's support line (or use their online lookup if they have one), give them the serial number, and they'll pull up the full spec sheet for your exact unit. Slower than the other methods, but it's the definitive answer.

3. Peek at the breaker size

Open your electrical panel and find the breaker labeled for the AC or condenser. A 20–30 amp breaker usually serves a 1.5 to 3 ton unit, while 35–50 amps suggests 3.5 to 5 tons. Of all three methods this is the fuzziest, since electricians size breakers with margin. Treat it as a sanity check, not an answer.

And if the unit is so old or unlabeled that nothing works? Flip the problem around: figure out what size the space actually needs with our AC tonnage calculator. If your mystery unit struggles to keep up with that number, it's probably undersized, and you'll want the right size anyway when it's time to replace it. Pricing that replacement? The AC unit replacement cost calculator turns your tonnage into a 2026 installed price.

Does the Indoor Unit Show the Same Tonnage?

Often, but not always, and this catches people who can only read one of the two plates. The indoor coil or air handler carries its own capacity code, and installers commonly fit one that is the same size as the outdoor unit or half a ton larger. So an air handler reading 042 can be paired with a 036 condenser, and the system is still a 3 ton system.

A gas furnace is a different matter. The number in a furnace model number is heating input in thousands of BTU, so 080 means 80,000 BTU of heat and says nothing about cooling. Some furnaces add a letter or digit for the blower size, which hints at the tonnage it can serve, but it is a hint only.

Tip: HVAC tonnage by model number means the outdoor unit's model number. Use the indoor plate only when the outdoor one is unreadable, and treat its answer as within half a ton.

AC Model Number Lookup vs Serial Number Lookup

The two numbers on the plate answer two different questions, and it saves time to know which one you need. An AC model number lookup tells you what the unit is: its size, its product line and usually its efficiency class. The decoder at the top is an AC model number decoder for the one part most people want, the size. It does the job of an air conditioner model number lookup, an AC unit model number lookup or an HVAC model number search, and to look up an AC unit by model number you only need the string from the plate.

An AC serial number lookup tells you when the unit was made, whether it is written as an air conditioner serial number lookup or an AC unit serial number lookup. The first few characters normally hold the year and the week or month of manufacture, in an order that changes from one maker to the next. That is the number to use when the question is the age of the system or whether it is still under warranty.

So for tonnage, search the model number. For age, search the serial number. An HVAC model number lookup on the manufacturer's site, or a call to their support line with both numbers, returns the full specification sheet when you need more than the size.

Found Your Tonnage? Here's What to Do Next

Knowing your unit is, say, 3 tons is only half the story. The more useful question is whether 3 tons is what your home actually needs. Plenty of houses in the US are running units that were sized by guesswork decades ago. Run your room or home through our AC Unit Tonnage Calculator and compare. If the numbers are far apart, that explains a lot about high bills or rooms that never feel right.

Need the same number in different units? The Ton to BTU converter flips between tons and BTUs instantly. And if you just discovered your unit is old enough to vote, our SEER savings calculator will show you what upgrading to a modern high-efficiency unit would save you per year, and the answer is usually more motivating than you'd expect.