A flooring calculator comes down to three steps: multiply the room length by the width, add 5 to 15 percent for cuts depending on the layout, and divide by the square feet printed on the box. Always round up to a whole box. A 14 x 12 ft room with 10 percent extra needs about 185 sq ft, which is 10 boxes of flooring that covers 20 sq ft per box.
The calculator works for laminate, vinyl plank, engineered wood, and solid hardwood, or any floor sold by the box.
How to measure a room for flooring
- 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.
- 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.
- Add closets, alcoves, and hallways. If the new floor runs into them, measure them as separate rectangles.
- 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.
- Read the box. Every box of flooring lists its coverage in square feet. Enter that exact number, decimals included.
- Pick the waste allowance. Use the table below. The calculator defaults to 10 percent.
The formula (with a worked example)
- Floor area = length x width
- Area to buy = floor area x (1 + extra % / 100)
- Boxes = area to buy / coverage per box, rounded up
The calculator's defaults describe a 14 x 12 ft room, flooring at 20 sq ft per box, and 10 percent extra:
- Floor area: 14 x 12 = 168 sq ft
- Plus 10 percent: 168 x 1.10 = 184.8, shown as 185 sq ft
- Boxes: 184.8 / 20 = 9.24, rounded up to 10
- Coverage bought: 10 x 20 = 200 sq ft
The calculator shows "Buy 10 boxes of flooring." and "Floor area: 168 sq ft, 185 sq ft with 10% extra. Boxes cover 200 sq ft." That last number is worth checking. Here you are buying 32 sq ft more than the floor, about 19 percent, because rounding up to whole boxes adds to the 10 percent you asked for.
Doing several rooms with the same floor?
Add the areas of all the rooms first, then apply the waste allowance and round up once. Rounding each room to whole boxes separately can leave you with a partial box of slack in every room. For example, three 10 x 10 ft bedrooms need 6 boxes each of 20 sq ft flooring when figured one at a time, 18 in total. Figured together, 300 sq ft plus 10 percent is 330 sq ft, which is 17 boxes. Just keep the extra percentage honest if one of the rooms is full of angles.
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:
| Situation | Extra to add |
|---|---|
| Hardwood, straight layout | 5% |
| Laminate, straight layout | 5% |
| Lower-grade wood, or picking boards for looks | 10 to 15% |
| Laminate on a diagonal | Add 10 to 15% |
| Hardwood on a diagonal | Add 15% |
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.
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.
| Room size | Floor area | With 10% extra | 15 sq ft boxes | 20 sq ft boxes | 25 sq ft boxes |
|---|---|---|---|---|---|
| 10 x 10 ft | 100 sq ft | 110 sq ft | 8 | 6 | 5 |
| 12 x 10 ft | 120 sq ft | 132 sq ft | 9 | 7 | 6 |
| 12 x 12 ft | 144 sq ft | 158 sq ft | 11 | 8 | 7 |
| 14 x 12 ft | 168 sq ft | 185 sq ft | 13 | 10 | 8 |
| 16 x 14 ft | 224 sq ft | 246 sq ft | 17 | 13 | 10 |
| 20 x 15 ft | 300 sq ft | 330 sq ft | 22 | 17 | 14 |
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.
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.
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.
Frequently asked questions
How many boxes of flooring do I need for a 12 x 12 room?
A 12 x 12 room is 144 sq ft. With 10 percent extra, you need about 158 sq ft. At 20 sq ft per box that is 8 boxes. At 19.63 sq ft per box, the coverage of one Pergo Outlast+ laminate, it is 9, because 8 boxes would cover only about 157 sq ft.
How much extra flooring should I buy?
For a straight layout in a simple room, 5 to 10 percent; Hosking Hardwood puts the baseline at 5 percent for both hardwood and laminate. For lower-grade material, rooms with many corners and closets, or diagonal layouts, plan on 10 to 15 percent or more. The calculator defaults to 10 percent.
Do I round up to a full box?
Yes. Flooring is sold by the box, so always round up. The calculator does this for you and shows how many square feet the boxes you buy will actually cover.
Should I include closets and hallways?
Yes, if the flooring runs into them. Measure each one as its own rectangle, add it to the total, and use our square footage calculator for rooms with odd shapes. Small, cut-up spaces waste more, so lean toward the higher end of the waste range.
Does the expansion gap mean I need less flooring?
Not in any way that matters. Floating floors need a gap at the walls (Pergo Pro specifies 3/8 in and Mohawk SolidTech 1/4 in), but it is a tiny strip compared with the room. Keep measuring wall to wall.
Should I keep leftover flooring?
Yes. Hosking Hardwood recommends keeping a carton or two for future repairs. A damaged plank is far easier to replace with a matching one from the original order than to match years later.