Watts from time

Does anyone know how I can back calculate watts (with reasonable accuracy)?

I did Challenge Peguera (race report to follow…)yesterday and in pre ride I thought my power meters numbers were very off (hadn’t calibrated properly after the flight?) - my race data, to my mind, only confirms this.

(2.46 on a hard correct distance course with almost no flat, 900+m (at the lowest count) of climbing, no drafting packs, my usual heavy TT bike and an NP of 175W - I don’t think so…)

So what I really want to do is put a course into a website, I guess enter some details about me and my bike, and my time/speed and find out what watts it thinks I did.

I’ve had a look at BBS briefly but not having used it before I can’t see how to do this - it wants to put in watts and give me time.

Guided by a friend managed to back out a BBS watts from goal time etc.
207AW/216NP. perhaps a smidge high but much more like it.

With BBS you’d need to use a known “good” file, with equipment and everything else as close to the recent race as possible. Then you can get it to estimate your cda.

Once you have a cda value, you have two options in a new race plan. Plan by watts, or plan by goal time. If you use the latter, it should give you a guide to how many watts are needed to ride that time. It’ll be idealistic in terms of power delivery, so unless you hit the VI it predicts, it’ll be a little different, but a good starting point

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