Although md suggests aiming for T-90, I have to say, PEK the last few times has been exceptionally busy. And I get to skip the check-in line because of status.

And the 45 minute estimate for taxi travel time is pretty optimistic, especially when heading to the airport. I'm not a super frequent traveller: I average 1-2 trips a month out of PEK. But that's quite a few flights on aggregate. There have definitely been more than a couple of times when I've only just made it with a couple of minutes to spare, even though I aim to get to the airport at T-120. This is because a single snarl up on the highway due to an RTA adds 10-30 minutes to the journey due to the peculiarities of Chinese law for road accidents.

One final caveat: don't assume if you 'book a taxi' at say 08:00, it will be there at 08:00, so you need to factor in the time for a taxi/ car to actually arrive at the hotel lobby. In Wangfujing, this is non-trivial, since taxis can earn much more by scamming clueless tourists than relying on meters.

tb