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).
However, some water-based paints are easier to work with than others. The first coat of paint may not provide complete wall coverage, or the color may not be quite as saturated. Some of these problems can be addressed with a separate primer coat, but this is a time-consuming project. The ideal solution is using a higher-quality paint that combines a primer and a finish paint in a “one coat” product.
Expect to pay between $600 to $3,500 or $1.25 to $3 per square foot to coat vinyl, with prices likely increasing for the finish. It is one of the more inexpensive siding materials to have repainted, especially with recent innovations in materials. Changing the finish on your siding is not recommended unless it's completely degraded and worn away by the weather. You can save nearly half the vinyl siding installation cost of $4 per square foot by painting rather than replacing. Before adding a new coat to vinyl siding,