Please note: For your convenience, this calculation has been rounded up slightly.

Important reminder: Every effort has been made to ensure the accuracy of this calculation. But before purchasing materials for any project, please check amounts with your suppliers or contractors.

In creating this calculator, we assumed certain average conditions. Your actual coverage depends upon many factors, including oddly shaped surfaces and your own drywalling skills. For your own peace of mind, consider buying 5-15 percent more drywall and supplies than you think you'll need. Also: be sure to have your plans approved by your local building department, and that you understand local codes regarding installation of drywall.

The sum of all the lengths of the room's walls. Don't deduct for doorways and windows.

This assumes that all walls are the same height and that the wall tops run horizontally. If this is not the case, you should manually figure each wall's area separately. For triangular and semicircular areas, multiply the largest height and width dimensions.

This assumes you have a flat ceiling. Do not depend on this calculator if your ceiling has obstructions that must be boxed before being drywalled.

Use this box for large deductions like sliding glass doors and solid-wood paneled walls. (Check building codes carefully -- you may need to install drywall before installing paneling or other surface materials.)

Panel waste depends on many factors, but particularly the complexity of the areas being covered. For basic flat walls with few openings, assume a waste factor of 10 percent. For highly complex installations, allow 20% waste factor.

Drywall comes in a variety of sizes. Larger sheets (4x10-foot or 4x12-foot) may allow fewer joints and smoother results.

Assumes standard ring-shanked drywall nails. Check with your supplier if you will be using drywall screws.