Hardwood flooring calculator

How this calculator works

It multiplies length by width, adds any closets or extra area, and adds a waste allowance for end cuts, defects and boards you set aside for color. Then it divides by the coverage on the box and rounds up to whole boxes.

For unfinished boards it also figures the floor finish: net floor area times the number of coats, divided by the coverage on the can, rounded up to gallons and quarts.

Worked example

An 18′ × 14′ dining room is 252 sq ft of floor. With 10% waste you need 277.2 sq ft, which at 20 sq ft per box is 13.86 boxes, so the list buys 14 boxes (280 sq ft). One 400 sq ft roll of felt covers the subfloor. If the boards were unfinished, three coats at 500 sq ft per gallon would take 1.51 gallons, bought as 2 gallons.

Tips before you buy

• Bring the boxes into the room and let the wood acclimate for as long as the maker recommends, often several days. Check the moisture of the wood and subfloor before you start.
• Rack out the floor: lay out boards from several boxes so lengths and colors are mixed before you nail them down.
• Leave the expansion gap the maker specifies at every wall. Solid wood moves across its width with the seasons.
• Keep a box or a few spare boards. Lots vary in color, and a matching board later is much easier from your own stock.

Questions

How much extra hardwood should I order?

Plan on 10% extra for a straight lay in a regular room. Diagonal layouts, herringbone and rustic grades with more knots and short pieces need 15% or more, because more boards are cut or culled.

How many square feet are in a box of hardwood?

It varies widely with board width, thickness and length, commonly about 15 to 30 square feet per box. The exact figure is on the box label and the product page, so enter it for an exact count.

What goes under nail-down hardwood?

Solid hardwood nailed to a wood subfloor usually goes over 15 lb asphalt felt or a similar paper, which slows moisture and reduces squeaks. Floating engineered floors use a foam or cork pad instead. Use what the flooring maker specifies.

How much finish does unfinished hardwood need?

Most floor finishes are applied in two to four coats, and a gallon typically covers around 400 to 600 square feet per coat. The calculator defaults to three coats at 500 sq ft per gallon; change both under Coverage and waste to match your can.