It's all fairly gentle. The grade on the Northampton rail trail from King Street (Route 5) to Leeds ranges between flat and around 2.5%; the average is 0.9%. The grade from the Connecticut to Amherst is similar; the steepest bit is from South Maple Street in Hadley to Route 116 in Amherst, but it's still not bad. The only other climb is on the Manhan Rail Trail, up and over the bridge that crosses Route 10, since there had been a grade crossing there when it was a railroad. But again, it's memorable only because the rest of the trail is so flat!