How much yarn will 4 oz of roving make?

This is the number one question I get asked about spinning from non-spinners. And I may add it was my number one question also before I had some experience with this spinning thing. I bought 4 oz of fiber at NW Handspun Yarns in Bellingham, WA. A wonderful yarn store owned by my friend Meg Jobe. Meg has a great collection of spinning & knitting supplies and is very knowledgeable about spinning and fibers. I loved the shop and sat upstairs knitting with some good friends.

But how much yarn will 4 oz of fiber yield?

I would say it's a DK weight two ply that I am most comfortable spinning and it yielded 285 yards of yarn. Now to decide what to make? I will probably use it as an accent color because it has some wonderful shiny stuff in it.