You might pay an additional $1 to $5 per square foot for optional repairs and updates. Consider having your molding, trim and baseboards checked while you have a professional in your home. This might be a good time to upgrade or repair any cracks, warps or other issues. Pros can usually touch up or replace these items for an affordable rate, and they may even package such fixups with your project.
For walls, measure the linear feet of wall space (measuring along the baseboards) for the areas to be painted (using a tape measure, laser, or both). Then multiply this by the ceiling height (usually it is 7.5 or 8). If there are 2 story areas, measure them separately, and multiply them by double the regular wall height. Then multiply the total number by 2 (for 2 coats).
One important consideration when comparison shopping for interior paint is the manufacturer’s available palette. One brand of latex paint may be significantly less expensive than others, but the tint options can be limited. There can also be a noticeable difference between one manufacturer’s “midnight blue” and another’s “Prussian blue.” There is no universal standard, so this is why sample cards and test paints are so important.

Dirt and grime are bound to develop on exterior house paint after some time. Luckily, you can easily clean your home with a pressure washer. It’s recommended that you pressure wash your home about five or six years after the initial paint job. For areas like porches and overhangs, you should clean them more often. Taking a garden hose to these areas once a year should do the trick.

Painting exterior windows depend on the size of the window and the number of panes. To calculate the price for windows larger than 15 sq. ft., add 1’ to each side of the window and then multiply width x length. Add two sq. ft. for each window pane for painting the mullions, muntins, and sash and then multiply your total sq. ft. by $84/100 sq. ft. So a 4’ x 4’ window with 4 panes will come to a total of 44 sq. ft. x $84/100 sq. ft. = $37.

The Cutters. Someone with meticulous attention to detail and a steady hand should be assigned the job of "cutting in," or painting a straight edge where needed, such as along a wall where the ceiling does not get painted. Many products are available to assist, but none work as well as a person who's good at doing it freehand. Ensure this person is skilled (ask them to show you). A poor, jagged, wavy or splotched cutting-in job will jump out at you every time you walk by it. Why more than one cutter? This job is nerve-wracking and painful to hands and arms after a few days. You'll want to give this person a break after a few walls.
After you have done the multiplication, subtract about 40 sq feet per window, and about 60 sq feet per door. Divide by 400 (interior paint covers 400 sq feet per gallon). The number that remains, is how many gallons you will need. If doing multiple wall colors, then you should do this process for each room (or sets of rooms) with a particular color. 
Many new homeowners want to change the color scheme of their rooms, either as a way to personalize the space or match the walls with existing furnishings and artwork. Interior house paint is relatively inexpensive, and it doesn’t require complicated machinery or professional-level skills to apply. There are also thousands of customizable colors available, as well as a choice of finishes, such as matte, semigloss, or gloss.

Wood is probably the most time-consuming when it comes to preparing it for paint. It has to be scraped and sanded until there isn’t a single chip or bit of loose paint in sight. Any wood siding or trim with wood rot will need to be replaced, and all cracks and holes need to be filled with epoxy filler. Brush painting and roll painting wood siding costs $43 per 100 sq. ft., and spray painting costs $34 per 100 sq. ft.
You’ll spend between $500 and $3,000 or $1 to $3.50 per square foot to paint concrete. However, expect to pay $2 to $7 per square foot since concrete almost always needs a coat of primer first. Double that price if the concrete requires stripping. Concrete is porous. Sealing it not only helps blend foundations and walls with your home’s aesthetic, but also seals it against water. Repairing or resurfacing concrete costs $300 to $500 for every 100 square feet.