Printing - DPI question

i have some photos i want printed at fairly large sizes - 16x20 inch
what DPI should i create the files at to have photo quality ?
i was thinking 6000x4800 pixels gives 16x20 @300dpi
i realise it will be a pretty large file, thats not a problem i was just wondering how many pixels wide and high i should output the finished files as

Ask your lab. In general letting them upsize is the better option. If you want to do it yourself tell photoshop 16x12" and 300ppi and let it worry about it. dpi is irrelevant - ppi moreso.