Flooring Calculator: How Much Flooring Do I Need?

How to measure a room for flooring

1. Measure length and width at the longest points. Go wall to wall, not baseboard to baseboard, and round up to the next half foot. The small extra is part of your safety margin. If you are painting too, the paint calculator uses the same length and width plus the wall height.
2. Split odd shapes into rectangles. An L-shaped room is two rectangles. Measure each, find the area of each, and add them up. Our square footage calculator handles up to three areas at once.
3. Add closets, alcoves, and hallways. If the new floor runs into them, measure them as separate rectangles.
4. Leave out areas the floor will not cover. Kitchen islands, built-in cabinets, and tubs sit on their own footprint. Check your product's instructions for what can and cannot sit on a floating floor.
5. Read the box. Every box of flooring lists its coverage in square feet. Enter that exact number, decimals included.
6. Pick the waste allowance. Use the waste tables below. The calculator defaults to 10 percent.

How to measure an L-shaped room, closets, and hallways

271 sq ft of floor in the example below. Split the room into rectangles that do not overlap, multiply length by width for each, and add them up; then subtract anything the new floor will not run under. MP Global Products' measuring guide says to subtract big permanent objects such as a kitchen island "before you account for waste," using a 3 x 5 ft island (15 sq ft) as its example.

Measure the leg of the L from where the main rectangle ends, so no strip is counted twice. With 10 percent extra, 271 sq ft becomes 298.1 sq ft: 15 boxes of 20 sq ft flooring. A closet and a hallway mean extra cuts; at 15 percent it is 311.65 sq ft, or 16 boxes. The calculator takes one length and one width, so enter 271 as the length and 1 as the width; with 10 percent it shows "Buy 15 boxes of flooring." Underlayment covers the same 271 sq ft: MP Global notes that most underlayment comes in rolls of 100 sq ft and advises allowing 10 percent waste, so that is 3 rolls.

How much extra flooring to buy

The right waste factor depends on the layout, the material, and the room. Hosking Hardwood's measuring guide gives these figures:

Why do diagonal layouts waste more? Hosking Hardwood points to the larger angled pieces cut off the boards at the walls. Rooms with many corners, closets, and doorways also mean more cuts, so push toward 15 percent there. The calculator defaults to 10 percent, between the straight-layout and diagonal figures; lower it only for a simple room laid straight. For a tile floor, the tile calculator counts tiles and boxes with its own waste figures.

Waste factor by layout: straight, diagonal, herringbone

15 percent for herringbone or chevron, against 10 percent for plain plank, in a floor under about 1,076 sq ft (100 m²): that is Havwoods' wastage guide, which drops the figures to 12 and 7 percent for larger floors. Shaw's herringbone installation guidelines start from a 5 percent cutting allowance and say diagonal, herringbone, or bordered installations "will require a higher percentage." Here is what each figure means for a 20 x 15 ft room (300 sq ft) in boxes of 20 sq ft:

Herringbone and chevron waste more because, as Havwoods puts it, the precise cuts mean "offcuts are less likely to be reused." Enter the figure in the calculator's Extra for cuts field: a 20 x 15 ft room at 15 percent shows "Buy 18 boxes of flooring."

Boxes of flooring by room size

This chart uses the calculator's formula with 10 percent extra. Box coverage varies a lot between products, so it shows three common-looking sizes. Use your actual box number in the calculator.

Small differences in box coverage can change the count. Pergo Outlast+ Marigold Oak, for example, covers 19.63 sq ft per case. For a 12 x 12 room that means 9 boxes, not 8, because 8 boxes cover only about 157 sq ft.

Square feet per box: laminate, vinyl plank, and hardwood

16.12 to 31.39 sq ft per box in the product listings below, so the same 12 x 12 ft room takes 6 boxes of one floor and 10 of another. Each count uses the calculator's formula with 10 percent extra, rounded up to whole boxes:

Coverage is from Pergo's and Shaw's product pages, Bruce's unfinished solid hardwood sell sheet, and The Home Depot's listings. Two Bruce floors differ by up to 12.89 sq ft per box, so read your own label rather than assume a size. The 6.14 in Outlast+ comes with its pad attached, so it needs no separate underlayment (see Underlayment below).

Random-width hardwood: how much of each width

25, 33.33, and 41.67 percent of the square footage for a mix of 3, 4, and 5 in boards. Wood Floor Business gives the formula as "(Total ft² / Total of widths used) x Width in question = ft² of width in question" and says to add at least 5 percent waste for each width. The formula gives every width the same linear footage, so the wider boards cover more of the floor. For a 300 sq ft room plus 5 percent (315 sq ft):

Use the calculator for the room's total, then split the total by width with the formula when each width comes in its own boxes or bundles.

Installation specs that affect your order

A few requirements from manufacturer instructions change how you plan the floor, even if they do not change the square footage much.

Expansion gap

Floating floors need space to move at every wall. Pergo Pro's installation instructions call for 3/8 in on all sides, and Mohawk's SolidTech vinyl calls for 1/4 in (5/8 in in spaces that get hotter than 85°F). Baseboard or shoe molding usually hides the gap; see our baseboard calculator if you are replacing trim at the same time.

Acclimation

Mohawk's SolidTech instructions call for acclimating the flooring for at least 48 hours, with the room kept between 55 and 85°F. Pergo Pro's floor instructions say to acclimate the product in unopened boxes; if there is no time, the storage and installation spaces should differ by no more than 25°F and 20 percent relative humidity.

Subfloor flatness

Both sets of instructions allow no more than 3/16 in of unevenness over 10 ft. If your subfloor is worse than that, plan on leveling compound before you lay a single plank. Replacing the subfloor? See the plywood calculator.

Stagger, last row, and long runs

End joints need to be staggered: Pergo asks for at least 12 in between end joints in neighboring rows, and Mohawk at least 8 in with a random pattern. Mohawk also wants the last row to be at least 3 in wide, so measure the room width and plan the first row to avoid a thin strip at the far wall. Pergo Pro requires T-moldings in rooms 40 ft or longer in either direction and in doorways 4 ft wide or less.

Underlayment

Underlayment is bought by the square foot too, so the same floor area applies. If your planks have underlayment attached, Pergo's instructions say not to add another layer under them.

Common mistakes to avoid

• Rounding the box coverage. 19.63 is not 20. Enter the exact figure from the box.
• Using the same waste for every layout. Hosking Hardwood suggests adding 10 to 15 percent for a diagonal layout.
• Forgetting closets and transitions. Small spaces add area and extra cuts. Measure them.
• Running short mid-project. Hosking Hardwood notes it is better to over-order than to stop and reorder, and suggests keeping a carton or two for repairs.
• Skipping the flatness check. Both Pergo and Mohawk require leveling where the subfloor is off by more than 3/16 in over 10 ft. Check with a long straightedge before you buy, and add leveling compound to the list if needed.
• Forgetting the extras. Underlayment (unless it is attached), transition strips, and new shoe molding are separate purchases. Underlayment uses the same square footage as the floor.