How to use this flooring calculator
Measure the room's length and width at the widest points, wall to wall. Choose a waste allowance that matches your layout, then enter the coverage printed on the box, such as "20.5 sq ft per carton", and the price per square foot or square meter. The calculator rounds up to whole boxes, since you can't buy part of one, and shows how much floor those boxes will actually cover.
For an L-shaped room or an open-plan space, split the floor into rectangles, calculate each one, and add the box counts together. For closets and alcoves, add their area to the main room rather than treating them as separate jobs.
The flooring formula
Boxes = ⌈ length × width × (1 + waste %) ÷ coverage per box ⌉
The brackets mean "round up to the next whole number".
Worked example: a 15 × 12 ft living room with laminate laid straight. 15 × 12 = 180 ft². Adding 10% waste gives 198 ft². The boxes cover 20 ft² each, so 198 ÷ 20 = 9.9, which rounds up to 10 boxes covering 200 ft². At $3.50 per ft², that's $700 of flooring.
How much extra flooring should you buy?
Every installation creates offcuts at walls, doorways and around obstacles. Some pieces will also arrive chipped or have defects. The right allowance depends on the layout:
| Layout | Typical waste |
|---|---|
| Large rectangular room, planks laid straight | 5–7% |
| Standard room, straight lay | 10% |
| Diagonal tile, many corners, closets or doorways | 15% |
| Herringbone, chevron or intricate patterns | 20% or more |
Large-format tiles and natural stone can need more, because a single bad cut wastes a big piece. When in doubt, buy one extra box. Most stores accept unopened boxes back, and if you keep it, you'll have matching pieces for future repairs.
Tips before you install
- Check the lot or batch number. Color and shade can vary between production runs, so buy everything from the same lot.
- Let it acclimate. Laminate, vinyl plank and especially hardwood often need to sit in the room for 48 hours or more before installation. Follow the manufacturer's instructions.
- Don't forget the extras. Underlayment, transition strips, baseboard or quarter-round, and for tile, thinset, grout and spacers.
- Mix boxes as you go. Pull planks from several boxes at once so shade differences spread evenly across the floor.
Frequently asked questions
How do I calculate square footage for flooring?
Multiply the room's length by its width in feet. A 15 × 12 ft room is 180 ft². For odd shapes, split the room into rectangles, calculate each one and add them together, then add your waste allowance.
How much extra tile should I buy?
Buy about 10% extra for a standard straight layout and 15% for diagonal layouts or rooms with many corners. Herringbone and other complex patterns need 20% or more.
How many boxes of flooring do I need for 500 square feet?
With 10% waste you need 550 ft². At 20 ft² per box, that's 27.5, so buy 28 boxes. Coverage per box varies by product, so always use the figure printed on the carton.
Should I keep leftover flooring?
Yes. Keep at least a few pieces, or a full box for larger rooms, so you can replace damaged planks or tiles later with an exact match. Discontinued colors can be impossible to find a few years on.
Results are estimates. Box coverage and recommended waste vary by product; follow the manufacturer's installation guide.