I need a 220 outlet for a welder what wire size do I need for a 50amps?

12 gauge

With 50 amps 220 the wire size should be num 6.. Length of run will make a diferance also
Repost this is the electric section for more specifics
14 ga for 15 amp
12 ga for 20 amp
10 ga for 30 amp
Etc

Le

Sometimes the rating changes for different types of insulation. If you are buying cut to length at Lowe's or Home Depot, they give the amp rating for everything. For a longer run, you may still need the next size up. Tkrussel may give more on that. #12 is for 20 amps.