In one respect calculating your retirement benefit is relatively simple. You can, in theory, find everything you need on the Office of Personnel Management site:
But some other calculators are better organized, especially to take into account special circumstances such as law enforcement, firemen, etc. I recommend this one for quick checks and retirement “what ifs”.
RP’s advice for the day? Retire as soon as practical … waiting seldom is worth the small gains … my only regret is I waited several years longer than I needed to.