I think this will depend on how spacious you want it to be...are you looking for minimum dimensions?

Yes, just minimum except for the 4 feet wide.

Thanks, does that include any wall thickness surrounding the staircase or do I need to add that?

Those dimensions would not include any walls --

Sweeby is correct - no walls in my numbers. Remember - all any of us can do is give a rough estimate - your plans and staircase design and materials will all impact the final dimensions. Err on the side of caution when allocating space.

Thanks everyone.