Cool little hack, however, I'm not convinced of its accuracy. There are a lot of assumptions at play here. The biggest being that you need to be able to control exactly when you fall asleep.
I have no idea how long it normally takes me to actually fall asleep, and I think the average 14 minutes you refer to will highly vary among people. Basically the entire calculation is ruined if it takes a little longer than I expect to fall asleep. Plus, if I knew that I was being timed, that small sense of urgency would keep me awake.
Something like this, to give you a good starting point, combined with something like the SleepCycle iOS app, to get the wake-up timing more precise, seem like a great combination.
I have no idea how long it normally takes me to actually fall asleep, and I think the average 14 minutes you refer to will highly vary among people. Basically the entire calculation is ruined if it takes a little longer than I expect to fall asleep. Plus, if I knew that I was being timed, that small sense of urgency would keep me awake.