Rohirric scholars?

I'm working on a story and even with my Atlas of Middle Earth, I'm uncertain how far it is from Edoras to Helm's Deep, especially if someone is riding a horse. Would it take a couple of hours? A day? I'm setting this post-WR when everything is peaceful but after my last mistake with my dwarf-centric story, I want to get my details right. I could probably spend a couple of hours looking through my copy of LotR and figure it out, but thought some of you who've set a lot of stories in Rohan could assist me. Any help is appreciated. :)