My weight swings about 5 lbs on either side of an average depending on the recent pizza/beer intake in my diet. My FTP puts me on the cusp between B and A with my lighter days solidly in A at just under 4.09 W/kg but my heavier days solidly in B at 3.92 W/kg. I’ve had two good races in the last 90 days while lighter that place me in the A category on zwiftpower. One was when I was 76.2 kg and one at 77.1. This morning I weight in (had chicken wings and pizza yesterday) and I’m 79.3 kg.
So I assume the accepted thing to do is just race As even though my FTP for the next few days will be 3.9 W/kg and just work off the poor choice in diet from last night? Or do you weight in before each race, put your weight in Zwift, and base your category on your raw FTP wattage and current weight? (Maybe I should just fast for a day and knock it back down…)
Hi @John_Bowers, Zwiftpower uses the best 3 results in your past 90 days to set your category, so just go with whatever that is. Are you updating your weight in the app every day? I would just choose the average weight and stick with that, but some races may require actual weight-ins (I’m not good enough to qualify for any of those 
)
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So is Zwift power using your best three raw watts and dividing by your current kg or using your best three w/kg doesn’t matter what you currently weigh?
I believe they will use 95% of your best 20 minutes power and most likely that is then divided by your weight at the time of the event. I don’t believe they readjust anything in the past if you increase or decrease your weight.
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It takes your listed weight at the time of the ride/race, it’s fixed at that point. If your weight changes later Zwift does not recalculate old performances.
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