How long does it take to renew a US passport?
I believe it depends on the issuing authority, but usually about two weeks if you pay the fee to have it expedited. You really can't ask for a definitive time, because it also depends on how busy they are. I have friends who paid the fee and got their passports renewed in just under two weeks, but that was a few years ago.
If you were born outside of the US and the issuing authority is the US State Department, it can take longer. I was informed of this when I received my daughter's passport, she was born abroad.
If you are out of the country and renewing through your local embassy, give it several months either way. I recently got a renewal in Manila which took just under 10 days, and inquired if
that's the usual amount of time from most embassies and they said yes. But, don't let paperwork kerfuffles jeopardize your travel plans, or being abroad without a valid passport for a little while. Additionally, if renewing the passport for someone under the age of 16, bring pictures of them that show their growth from their last passport photo to their appearance now. The consulate might let you slide if the resemblance is uncanny, but be prepared - not having these could cause substantial delays.
To be safe, I'd allow at least two months. You might not be able to expedite it if you're out of the country, so keep that in mind. Otherwise, pay the extra fee, the worst that can happen is you get it sooner than expected.
That is of course if not having it renewed in time might put a dent in your travel plans.