How to use this calculator
Estimate floor area and material allowance. Enter length (feet), width (feet), extra material (%). The result updates when you change an input. To compare two sets of inputs, save scenario A, then enter the second set; the result panel shows the difference.
Formula and limits
Rectangular floor area = length × width. Material allowance = area × (1 + extra percentage ÷ 100). Openings and irregular shapes are not subtracted.
Worked example
The following example uses the calculator’s starting values. It is an illustration of the method, not a recommended target.
| Input | Example value |
|---|---|
| Length (feet) | 12 |
| Width (feet) | 10 |
| Extra material (%) | 10 |
Square feet: 120
With allowance: 132 sq ft
Interpreting your result
Confirm actual dimensions, supplier specifications, and site conditions. Quantity estimates do not establish structural adequacy or compliance with building codes. Waste allowances are user assumptions.
Comparing alternatives
Save the first result as scenario A, then change one input. The comparison shows the numeric difference; it does not label either result as better. Choose inputs that describe realistic alternatives. Values shown on screen are rounded, so calculations from rounded intermediate results may differ slightly.