How do I figure how much it will cost to paint the interior of my new house

Are you doing the work or hiring someone? If you hire they can give you an estimate in advance. If you do the work it would help to tell us the dimensions of the rooms. Most paints will require two coats so read the coverage on the can and double that amount and multiple by about $28. Brushes and drop clthes are neede but maybe you already own, right?

$3 a ft