Square footage = length (ft) x width (ft). For material ordering, add a waste factor: order quantity = square footage x (1 + waste %). Typical waste allowances run about 5% to 10% for straightforward rectangular layouts and 10% to 15% for diagonal patterns, complex rooms or material with a repeating pattern that has to be matched.
The math is simple, the waste factor is where jobs go wrong. Enter your dimensions to get area, the quantity to order after waste, how many boxes or sheets that is, and what it costs.
| Input | Value |
|---|---|
| Length | 20 |
| Width | 14 |
| Number of identical areas | 1 |
| Deductions | 0 |
| Waste factor | 10 |
| Coverage per box or sheet | 24 |
| Price per box or sheet | 62 |
| Result | Value |
|---|---|
| Net area | 280 sq ft |
| Order quantity with waste | 308 sq ft |
| Boxes or sheets to buy | 13 |
| Material cost | $806.00 |
| Cost per sq ft installed area | $2.88 |
| Square yards | 31.11 |
A rectangular room with straight-lay plank wastes far less than the same material run diagonally or in a herringbone pattern. Rooms with many jogs, angles or transitions cut more offcuts you cannot reuse.
Suppliers sell in whole boxes or sheets, so always round up. For tile, flooring and shingles, buying the shortfall later risks a different dye lot or batch that visibly does not match.
Leaving a box or two on site for future repairs is cheap insurance and reads as professional. Build it into the estimate rather than eating it.
Multiply length by width in feet. For rooms that are not rectangular, split them into rectangles, calculate each one and add the results, then subtract areas you are not covering.
Around 5% to 10% for straight-lay installations in simple rectangular rooms, and 10% to 15% for diagonal or patterned layouts, irregular rooms or material requiring pattern matching. Check the manufacturer's guidance, since some warranties assume a minimum allowance.
Nine. Divide square feet by 9 to get square yards, which is how carpet and some other floorcoverings are still priced.
WinkScope's free square footage calculator computes area (length x width x number of areas, minus deductions), applies a waste factor, and converts to boxes or sheets and material cost. Waste allowances typically run 5% to 10% for straight rectangular layouts and 10% to 15% for diagonal, patterned or irregular installations. One square yard equals nine square feet. Free, no signup.