Can I wire two 21.7/amp ovens by running one # 6/3 to a j box.from the main with a 50 amp breaker . Or do I have to run two separate 10/3 or 8/3 from the main with a 30 or 40 amp breaker. Thanks pap71

What are the amprage draw of most built in ovens

There are so many different ovens, a good answer is to look at the spec sheets of ones in which you may be interested. Size, features, Wattage and Voltage would make the amperage vary.

You can feed a box with two breakers inside, one 25-30 amp breaker to each oven. The breaker from main box should be the total of the two in the feeder box. Make sure the breakers match the wire size. 10-3 is too small. Use 6-3 or 8-3 wire at a minimum. 6-3 should feed the box and you can use 6-3 to feed each oven. DrTom4444

They vary. Look at the name plate. DrTom4444