Flooring Calculator: Square Feet & Boxes Needed
Work out how much flooring to buy for one or more rooms — square footage, boxes, underlayment and total cost — with a waste allowance for your layout.
A 12 × 12 ft room (144 sq ft) needs about 154 sq ft of flooring with 7% waste, which is 8 boxes of 20 sq ft. Formula: length × width × (1 + waste %) ÷ coverage per box, rounded up. Use 15–20% waste for diagonal or herringbone layouts.
Your numbers
Result
How to calculate how much flooring you need
Measure the length and width of each room, multiply to find square footage, and add waste. For rooms that aren't rectangles, split them into rectangles, measure each, and add the areas together.
flooring to buy = area × (1 + waste %)
boxes = flooring to buy ÷ coverage per box (round up)
Flooring needed by room size (7% waste)
| Room size | Area | With waste | Boxes of 20 sq ft |
|---|---|---|---|
| 10 × 10 ft | 100 sq ft | 107 sq ft | 6 |
| 10 × 12 ft | 120 sq ft | 128 sq ft | 7 |
| 12 × 12 ft | 144 sq ft | 154 sq ft | 8 |
| 12 × 15 ft | 180 sq ft | 193 sq ft | 10 |
| 14 × 18 ft | 252 sq ft | 270 sq ft | 14 |
| 15 × 20 ft | 300 sq ft | 321 sq ft | 17 |
| 20 × 25 ft | 500 sq ft | 535 sq ft | 27 |
Waste factors by layout
| Layout | Typical waste |
|---|---|
| Laminate, vinyl plank, hardwood (straight) | 5–10% |
| Tile (straight) | 10% |
| Diagonal | 15% |
| Herringbone, chevron, patterned | 15–20% |
| Rooms with many angles or closets | +5% |
Don't skip the spare box
Flooring lots can vary in color and finish. Ordering a little extra up front means you'll have matching material for future repairs, and you won't be stuck with a discontinued product. Let boxes acclimate in the room for 48 hours before installing hardwood or laminate.
Other flooring materials
Tiled floors have their own formula that includes grout joints — use the tile calculator. For wall-to-wall carpet, which is sold by the square yard from a roll, use the carpet calculator. Baseboard and shoe molding are counted by linear foot in the baseboard calculator.
Frequently asked questions
How much extra flooring should I buy?
Buy 7–10% extra for most installs, 15% for diagonal layouts, and 5% for large, simple rooms.
How many square feet are in a box of flooring?
It varies by product — laminate and vinyl plank boxes commonly cover 18–25 sq ft, hardwood 15–25 sq ft. Check the box label.
How much flooring do I need for a 12×12 room?
A 12×12 room is 144 sq ft; with 7% waste you need about 154 sq ft, or 8 boxes of 20 sq ft.
Do I measure inside closets?
Yes. Measure each closet or alcove separately and add it to the total. The same goes for hallways and under appliances you won't move.
How do I measure an L-shaped room for flooring?
Divide it into two rectangles, find each area, and add them.
Do I need underlayment?
Most laminate and engineered floors need it; some vinyl planks have it attached. Follow the manufacturer's requirement.
How much does flooring cost per square foot?
Laminate and vinyl plank commonly run about $1.50–$5 per square foot for materials, hardwood $4–$12 and tile $2–$15, varying by quality.
Does stair flooring use the same formula?
No. Stairs are priced by tread and riser. Measure the number of steps and the depth and width of each, and add 10% extra.
Sources and further reading
- National Wood Flooring Association — NWFA: wood flooring installation guidelines
These references support the general guidance on this page. The calculator applies the standard formulas shown above to the numbers you enter.
Related calculators
. Estimates only. Always confirm quantities with your supplier or a qualified contractor before ordering, and add extra for waste and site conditions.