Day trip to Kalmar from Stockholm?

How would you be traveling? From Stockholm to Kalmar it's about 5 hrs each way by train or driving, a little over 6 hrs on the bus. You could fly between the 2 in about 3 hrs but then how would you get around Kalmar? If you're driving from Stockholm to Copenhagen (or vice versa) it would be better done as a one-night stopover, or if you don't want to spend the night it could be done as a lunch stop between the two and you could just spend 2-3 hrs in Kalmar.

It is too far for a day trip.

If you are looking for a day trip from Stockholm and want to see an interesting castle, consider Gripsholm Castle in Mariefred.

Thank you both for the feedback -- I guess if we decide Kalmar is a high priority, we'll need to "attack" it as we're en route between Cope & Stock, possibly spending a night.

Several years ago, we took the train from Stockholm to Kalmar - spent a couple nights there. At Kalmar we rented a car - saw Oland Island and from there drove to Copenhagen. We liked Kalmar.