Originally Posted by
Brightwork
By no means is it bang on, but it will give you a rough idea - assuming you put the correct figures in.
It's definitely not "bang on". In fact it seems pretty inaccurate. Which is to say: I own a PowerTap Pro+ power meter and a Garmin Edge 705 and the numbers they produce never seem to match the website.
To answer the original question: I'm down to a svelte (for me) 175lbs. Last time I did a test, ages ago, my FTP (Functional Threshold Power) was around 240 watts. During an all-out sprint, I think the highest number I've seen was around 980 watts... and that was only for a few milliseconds, I'm sure!