A complete reference PDF can be downloaded HERE:  Trane PDF

You can determine tonnage of equipment based on numbers that can be divided by 6 or 12. You can almost always find these numbers somewhere in the middle of the model number.

Tons can be determined by the 3rd and 4th  numerical digits in the center of the model number for Trane. (after letter sequence)

Other factors can also help determine the size. Other considerations should be:

• Sq Ft of the home.
• Electrical amperage requirements.
• Sizing at the condenser.

 A standard numerical chart is listed below for typical size references.