I am trying to run an electrical wire to power a 5 ton central air - 220/40 volts - 40 amps.
Its length is approxaimately 60 feet from the panel - what type /wire gauge do I need?

Personally, I' a little puzzled by the length of your run. Are the compressor and motor located in the roof of your dwelling? You need to size your conductors to get your conductor size correctly. Is this a new installation site or are all th3e sub requirements already rated and installed? For example is the Service Disconnect installed to code and inspected. Do you have the requisite permits for this installation. Have you sized and installed the concrete pad?

Fortunately, almost all of the electrical information is contained on the motor plate label. That gives us all manner of needed information. Would you consider putting the exact information from the label plate into this item so we can assist you?

I'll continue to assist once I get the needed information back from you

Number 8 copper will work BUT I am always heavy on electric feed for HVAC so I would roll with a number 6 copper. More capacity makes a compressor a happy camper. Now if it is a spec job be cheap. LOL