capaz, no cabaz.

Wait for some more help from others . . .

Well, which of the following is "the most correct"?

I ought to be capable of doing it tomorrow.
I ought to be able to do it tomorrow.

¿ está diciendo que ambos son correcto'.

douglas said:

¿ está diciendo que ambos son correctos'.

Sí.

If you're trying to say, "I should be able to do it tomorrow," I would go with, "Creo que puedo hacerlo mañana." It just sounds more natural. The other ways sound too literal and I don't think people generally express themselves like that.

LadyDi said:

If you're trying to say, "I should be able to do it tomorrow," I would go with, "Creo que puedo hacerlo mañana." It just sounds more natural. The other ways sound too literal and I don't think people generally express themselves like that. Of the two, however, the second one you proposed sounds the best to me.

Yes, I agree with what you say. That's why I used "ought," because it's a little unusual.

Douglas, "debo" is closer to "I must" than "I should," and that's another reason I used "ought."

As always, you'll get better answers if you give us the information we need to provide an answer (such as what it is that you are trying to say).