i live at the corner of a street with a +/- 20% grade. most directions i go, i’ll hit grades in the 15-20 range within a few blocks, but there are a handful of useful routes that keep it to 8% max.
when i head out to ride for fun, a few times a week, i’ll typically hit one or two or three long-ish sustained climbs, around 6 percent average for up to a couple miles, steepest bits in the 12% range, up to 2000’ feet bottom to top.