Incidentally, no math required. Check out the Planet Summary screen, and usually on the top right of the chart you'll see size of maintenance facility in tons.
I have 68 MF at the moment, which should be enough for all my overhauls. However I have a lot of ships in orbit at the moment - are the MFs considered in use if there are ships to maintain? NB I've been able to overhaul my smaller missile cruisers and escorts without a problem.
Shipyards are not the same as maintenance facility. You build MF from industry, and can track your level by looking at your summary tab, I believe it is one MF per 200 tons, so you are going to need something over 100 MF for your carriers.