Someone presented a couple of comparisons of inauguration attendance vs Women's March on Washington attendance (the latter had more people):
Busiest wide shot I can find of the #inauguration vs shot a minute ago from #womensmarch
People were more bunched… https://twitter.com/i/web/status/822861119178108930
For further comparison, here's a tighter shot taken just before #inauguration speech vs same zoom just now from… https://twitter.com/i/web/status/822862192777326592