Hey @Nbwilli,

When data from a power meter is unavailable, Strava can estimate power using information about an athlete's weight, speed, and elevation change. For more information, take a look at our support article here. 

@Nbwilli Additionally the bike weight and bike type will be used for the estimation. The bike type isn't even mentioned in the linked article, but MTBs will produce a much higher estimation for the same speed than i.e. time trial bikes when there is no gradient involved.

OK, that’s what I thought but how can my power be the same as a smaller person who went slower on the same ride?  Neither of us have identified our specific road bike models…

This could be due to wrong setup data for one or both of you for the mentioned variables.