Also the type of hospital.
One I worked in only had a couple of hundred beds but as it was a specialist cardiac centre with a large ITU the was a lot of complex equipment. So just going by numbers is not a simple process as Dave has said.
If you are coping now and the number of beds is going up by two thirds you need two thirds more staff.

My spelling is not bad. I am typing this on a Medigenic keyboard and I blame that for all my typos.