Rehab room calculations?

[Reggie Burnett]

I'm trying to come up with some simple per square foot room calculations for rehab.  For example it seems like sq footage divided by 10 gives a good estimate for number of 12 foot drywall boards needed for walls and ceiling.   For example, this equation for a 12x12 room would yield an estimate of 14 boards.  Then you multiple by your per board finishing cost.

I hope to do the same for hardwood, laminate, roofing, paint, etc.   Then I can put together a sq foot estimate for a room.  

For example, I want to be able to measure a bedroom that needs drywall, paint, trim, and flooring and come up with a quick estimate for the rehab.

Anyone got any numbers, equations, or estimating ideas they'd like to share?

Thanks!