Your AC's tonnage is coded into the outdoor unit's model number — usually as the capacity in thousands of BTU (24 = 2 tons, 36 = 3 tons). Paste the model number below, or pick your brand for the exact nomenclature.
| Capacity code | BTU/hr | Tons |
|---|---|---|
| 09 | 9,000 | 0.75 |
| 12 | 12,000 | 1.0 |
| 18 | 18,000 | 1.5 |
| 24 | 24,000 | 2.0 |
| 30 | 30,000 | 2.5 |
| 36 | 36,000 | 3.0 |
| 42 | 42,000 | 3.5 |
| 48 | 48,000 | 4.0 |
| 60 | 60,000 | 5.0 |
Each page explains exactly where the capacity code sits in that brand's nomenclature, with verified examples.
Two digits after the series letters are the capacity code in thousands of BTU.
→USCarrier condensers start with 24 (AC) or 25 (heat pump); capacity code follows the series letters.
→USDigits 7–8 in 4TT model numbers are the BTU code.
→USLennox uses a three-digit code after the series (e.g. -036).
→USRA-series: digits 5–6 are the capacity code.
→USSame nomenclature as Rheem (sister brand), UA prefix.
→USCapacity code follows the YC-series letter.
→USAmana shares Goodman nomenclature.
→USCarrier-family nomenclature; code after series letters.
→USCarrier-family budget line; PA prefix.
→BOTHUS DX-series uses BTU codes; Indian FTK-series uses kW-class codes (25=0.8T, 35=1T, 50=1.5T, 60/71=2T).
→USTrane sister brand; same digit positions.
→USICP family; capacity code embedded after series.
→INIndian convention: first two digits = tonnage×10 + star rating digit (185 = 1.5T 5★).
→IN12/13 ≈ 1 ton, 18/19 ≈ 1.5 tons, 24 ≈ 2 tons (thousands of BTU).
→INAR-series digits are thousands of BTU: 12=1T, 18=1.5T, 24=2T.
→INBTU-code digits inside the model string.
→INIndian Hitachi: middle digits encode star+capacity; 18-group = 1.5T, 12-group = 1T, 22/24-group = 2T.
→INCS-series digits are thousands of BTU.
→INFujitsu General; BTU-code digits after series letters.
→INGS/LS prefix + BTU code.
→INTonnage usually printed directly in the Indian model name.
→On the data plate (a metal or foil sticker) on the side or back of the outdoor condenser unit. Use the model number, not the serial number — the serial encodes manufacture date, not capacity.
The decoder falls back to scanning for standalone capacity codes (09, 12, 18, 24, 30, 36, 42, 48, 60) and shows every candidate it finds with a confidence note. If nothing matches, read the rated cooling capacity directly from the data plate — it's always authoritative.
Most manufacturers embed the capacity in thousands of BTU as a two- or three-digit group: 18 = 18,000 BTU = 1.5 tons, 36 = 3 tons, 60 = 5 tons. Indian brands sometimes use kW-class codes or print the tonnage directly.