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Calculation breakdown
These values reflect the editable inputs and assumptions above.
| Quantity | Value |
|---|
Calculation report
Includes formulas, entered assumptions, limitations and sources.
Compare scenarios
Keep up to three alternatives to compare measured values and assumptions.
Measure area before choosing a material#
Use this workbench when a project has more than one room, a curved section or a cutout. Choose a shape for each entry, add a repeat quantity for identical areas, and mark excluded sections as deductions. The main answer is the net measured area; material allowance and package counts appear separately.
Shape formulas and required measurements#
| Shape | Measurements | Area |
|---|---|---|
| Rectangle | Length and width | Length × width |
| Circle | Diameter | π × (diameter ÷ 2)² |
| Triangle | Base and perpendicular height | Base × height ÷ 2 |
| Trapezoid | Two parallel sides and perpendicular height | (Side A + side B) × height ÷ 2 |
| L-shaped room | Outer rectangle and missing corner | Outer area − cutout area |
Lengths in US mode are decimal feet. For example, 9 ft 3 in is 9.25 ft, not 9.3 ft. Switching measurement system converts existing dimensions and package coverage rather than relabeling them.
Worked example: an L-shaped room#
An outer rectangle measures 18 × 14 ft, with a 6 × 4 ft missing corner. Its net area is 252 − 24 = 228 ft². At a user-chosen 8% material allowance, the material quantity becomes 246.24 ft². If one package covers 20 ft², the purchase estimate is 13 packages.
The 228 ft² measurement remains unchanged. The allowance belongs to the material order, not to the geometry. Optional cost is price per area unit multiplied by allowance area, with entered fixed cost and tax; it does not price the rounded package count.
Avoid counting the same space twice#
An L-shaped entry already subtracts its corner. Do not add that corner again as a deduction. When splitting a room into rectangles, their interiors must not overlap. A circle uses diameter, while a triangle or trapezoid requires a height perpendicular to its base—not a sloping side.
For sloped roof surfaces use the Roof Pitch Calculator. For wall panels use the Drywall Calculator, whose purchase counts account for whole sheet sizes.
Sources and scope#
The conversion uses the international foot: NIST’s foot definition and NIST unit conversion factors. The shape equations are ordinary planar geometry. This is a measuring tool, not a determination of legal living area or appraisal eligibility.