How to use the flooring calculator
- Add a row for each room or area with its length and width in feet. Use Subtract for areas that will not be floored.
- Enter the coverage per box from the flooring carton, in square feet.
- Keep the 10% waste allowance or change it. Tick Include underlayment if you need it and enter the coverage per roll.
- Read the boxes to buy (rounded up), the exact figure, and the extra flooring you will have. Add prices for a cost estimate.
Formula
Floor area = sum of (length x width) for added rooms - sum for subtracted areas
Area with waste = floor area x (1 + waste percent)
Boxes = area with waste / coverage per box, rounded up
Underlayment rolls = area with waste / coverage per roll, rounded up
Flooring is sold by the box, so the answer is always a whole number. The exact figure is shown too, so you can see how close you are to the next box.
Worked example: two rooms of laminate
A living room 15 ft by 12 ft is 180 sq ft and a bedroom 10 ft by 10 ft is 100 sq ft, for 280 sq ft.
A 10% waste allowance makes it 308 sq ft. With boxes covering 20 sq ft each, that is 308 / 20 = 15.4, so you buy 16 boxes, which is 320 sq ft and 40 sq ft more than the floor.
Underlayment on the same 308 sq ft with 100 sq ft rolls is 3.08, so 4 rolls.
At $45 per box and $30 per roll the cost is 16 x $45 + 4 x $30 = $720.00 + $120.00 = $840.00.
Measuring rooms for flooring
Measure each room at its widest points and split odd shapes into rectangles. Closets, hallways and bay alcoves should be separate rows so you can see where the area comes from. Flooring usually runs through doorways, so you do not subtract them. Do subtract permanent features you will not floor, such as a kitchen island or built-in cabinets, because material is not needed under them.
If a room is not a rectangle, the square footage calculator handles triangles, circles and trapezoids.
Choosing a waste allowance
Waste depends on room shape, plank length, pattern and installer skill. Rooms with many corners, diagonal layouts and patterns that must line up all use more material. A starting allowance of 10 percent suits many plain layouts, and the field is editable so you can use the figure your installer or the manufacturer recommends.
Matching batches and spares
Flooring is made in production lots and color can vary between them. Buying all the boxes at once from the same lot avoids a visible mismatch. Keeping one or two unopened boxes after the job lets you repair a damaged board later. For tile, use the tile calculator, which accounts for grout joints.
Assumptions and limits
- The coverage per box is whatever you enter. The 20 sq ft starting value is not a standard, so use your carton.
- Rooms are rectangles that you measure. The waste allowance covers cuts, and it is your choice.
- Underlayment uses the same area with the same allowance and a roll size you enter (100 sq ft by default). Check the product, because some underlayments are sold in other sizes.
- Transitions, thresholds, molding, adhesive and subfloor repairs are not included.
- Cost uses only the prices you enter and does not include delivery, tax or installation.
Frequently asked questions
How many boxes of flooring do I need for 500 square feet?
With a 10 percent allowance you need 550 square feet. If each box covers 20 square feet that is 27.5, so 28 boxes. Enter your own coverage per box for an exact answer.
Should I subtract closets and doorways?
Include closets that will be floored and do not subtract doorways. Subtract only permanent features that will not get flooring, such as a fixed island.
How much extra flooring should I order?
It depends on the layout and the product. A common starting figure is 10 percent for straightforward rooms and more for diagonal or patterned installs. You set the percentage here.
Do I need underlayment under my flooring?
Some floating floors need it and some have it attached already. Follow the manufacturer instructions for your product and use the checkbox only when you need to buy it separately.
Why does the calculator show leftover flooring?
Boxes are sold whole, so you usually end up with more than the measured area. The leftover figure shows how much extra you are buying beyond the floor itself.