Originally Posted by
bampilot06
strava tells me mine is 181. But then I updated my weight because I lost another 10 pounds, and now it says 171. I would imagine I’m stronger even with the weight loss, and not really sure how they come up with this number.
It's a stack of assumptions and guesses. I'm fairly certain that they're just looking at your best 20-min power (probably within 6 weeks) and then taking 95% of that. If you don't have a power meter or a location suitable for that type of steady output (7+ mile stretch that's relatively uninterrupted), they're FTP estimate isn't going to be very good.