When I first started biking to work, I thought that my route was kind of hilly. Then as I developed some fitness I went along with the "rolling hills" description. Eventually I realized it's basically flat. Then I moved. Now I've got the same basic route, but with a real mean kicker at the end of the day.

My main route has a few bits that go as much as 3% for a few hundred feet, but it's mostly flat. The hill going up to my house, on the other hand, is about half a mile at 2-5% and then I can choose between a quarter mile climb that averages 9.3% and peaks at 20% or a half mile climb that averages 5.2% and peaks at 14%. MapMyRide puts either of these as a Cat 5, though strictly speaking I don't think either one is long enough to get a category rating.

MapMyRide, by the way, is terrible at calculating grade for short segments of longer rides. Something in its algorithm discards local variations, so if you have a hill that goes up 100 feet, down 50 feet and then up 100 more feet, MapMyRide will show you a constant ascent of 150 feet over the whole distance. If you want to see the local variations, you need to map just the segment you're looking at. For instances, the hills to my house show up as 2.9% average grade for either climb if I put them at the end of my 10 mile route, but as 5.2% and 9.3% if I map them by themselves. Neither of these climbs has any downward slope, but for whatever reason MapMyRide miscalculates the elevation at the bottom of the hill.

BTW, when I go up the steep side of my hill, I'm generally climbing at about 5 mph/8 kph.