How this calculator works
Enter your room’s length and width in feet to get its raw area. Then adjust the waste-factor slider to add extra material for cuts, offcuts, and defects, the amount actually recommended when you go to buy flooring.
The formula
areaSqFt = lengthFt x widthFt neededSqFt = areaSqFt x (1 + wasteFactorPercent / 100), rounded up to the nearest whole sq ft
Worked example
A 12 ft by 15 ft room, with a 10% waste factor:
- Room area: 12 x 15 = 180 sq ft
- Waste addition: 180 x 10% = 18 sq ft
- Total to buy: 180 + 18 = 198 sq ft
Frequently asked questions (FAQ)
How do I measure a room for square footage?
Measure the length and width of the room in feet, along the longest straight run of each wall, then enter those two numbers. For an L-shaped or irregular room, split it into rectangles, calculate each one's area separately, and add the totals together.
What waste factor should I use for flooring?
This Old House recommends adding 10% to your room's square footage to cover cuts and waste for a typical hardwood installation. That 10% default is a solid starting point for most straight-layout rooms; simple, mostly-square rooms can sometimes get by with less.
Do I need a higher waste factor for diagonal or herringbone patterns?
Yes. Angled layouts like diagonal, herringbone, or chevron patterns require more cuts and produce more offcuts than a straight layout, so flooring installers commonly budget noticeably more material for them. Move the waste factor slider higher, toward the 15-20% range, for these patterns.
Why does the calculator round the amount I need up to a whole number?
Flooring is sold in fixed units, boards, tiles, planks, or boxes, so you can't buy a fractional amount. Rounding the final square-footage-needed figure up to the next whole number ensures you order enough material rather than coming up just short.
Does square footage include closets or alcoves?
Only if you measure them. If a closet or alcove will also get the same flooring, measure it as its own rectangle and add its area to the main room's total before applying your waste factor, since the calculator only multiplies one length by one width at a time.
Can I use this for tile, carpet, or laminate too, not just hardwood?
Yes. The area formula and waste-factor logic work the same way regardless of material. Different materials and patterns call for different waste percentages, so check your specific product's installation guide and adjust the slider accordingly.
Sources
- This Old House: How To Install Hardwood Floors, which recommends adding 10% to a room’s square footage for waste and cuts.