How this calculator works
Floor area plus any closets is increased by your waste allowance and divided by the coverage printed on one box. The result is rounded up, because flooring is sold in full boxes.
Area = Length × Width + Extra
Boxes = round up( Area × (1 + Waste%/100) ÷ Box coverage )
Assumptions and tips
- Underlayment, transitions and baseboard are not included — see the Baseboard Calculator.
- Let flooring acclimate as the manufacturer directs before installing.
Worked example
Using the default values in the calculator above:
| Input | Value |
|---|---|
| Room length | 15 ft |
| Room width | 12 ft |
| Extra area (closets, nooks) | 0 sq ft |
| Waste allowance | 10 % |
| Coverage per box | 20 sq ft |
| Price per sq ft (optional) | $0 |
| Result | Value |
|---|---|
| Boxes to buy | 10 boxes |
| Floor area | 180 sq ft |
| Flooring purchased | 200 sq ft |
Step by step:
- Area = 15 × 12 + 0 = 180 sq ft
- With 10% waste = 198 sq ft
- Boxes = 198 ÷ 20 → 10
Boxes of flooring for common rooms
20 sq ft per box, 10% waste.
| Room | Boxes to buy | Flooring purchased |
|---|---|---|
| 10 × 10 ft | 6 boxes | 120 sq ft |
| 12 × 12 ft | 8 boxes | 160 sq ft |
| 12 × 15 ft | 10 boxes | 200 sq ft |
| 15 × 20 ft | 17 boxes | 340 sq ft |
| 20 × 25 ft open plan | 28 boxes | 560 sq ft |
Common mistakes to avoid
- Forgetting closets, hallways and under appliances.
- Not keeping a spare box for future repairs — matching later is hard.
Frequently asked questions
How much extra flooring should I buy?
Around 10% is typical for plank flooring laid straight; add more for diagonal layouts or rooms with many angles.
Do I include the closet?
Yes, if the flooring continues into it — add its area in the extra field.