A stage is where a guidebook author was tired. That's all it ever was. Somebody walked from Saint Jean to Roncesvalles in one go and wrote it down as Day 1. Centuries later, ten thousand people a season still walk that same day, because it has a number on it.
What stages cost you
The obvious thing is the bed race. If the book says everyone sleeps in Zubiri, everyone sleeps in Zubiri, and the albergue is full by noon. Four kilometres further on there's a village with beds, a bar and nobody in it, and it isn't in the book because it isn't a stage.
The less obvious thing is that stages are the same length for a 24-year-old and a 68-year-old, for someone with three weeks and someone with five. They were never designed for you. They were designed for the page count.
Every town with a bed in it is listed, and the distance between them. Where you stop is your business.
What the guides do instead
Every town on every route has its own page: the distance back to the previous place with beds and on to the next one, what's there, what the road in is like, and every albergue, pension and hotel with prices. Put those together and you have something a stage list can't give you: choice at four in the afternoon, when your feet are talking.
If you'd still like a starting point, there are sample itineraries for the Camino Francés. They're examples. Load one into the planner, then move things until it's yours.
“But how many days will it take?”
Divide the route length by whatever you comfortably walk in a day. For most people that's between 22 and 28 km, so the Camino Francés is 27 to 35 days, the Camino del Norte 30 to 38, before any rest days you decide to take. The planner does this sum for you, and re-does it every time you change your mind.
Compare every route if you haven't chosen one yet.
