How to measure a room for flooring
By Dexaloop · Updated 27 October 2026 · Checked against the sources listed below
To measure a room for flooring, split the floor into simple shapes (usually rectangles), multiply length by width for each one, and add them up. Then add a waste allowance for cuts, which depends on the product and layout, and divide by the area one box covers, rounding up to a whole box. Makers publish ranges such as 5 to 15% depending on the product, and patterned or diagonal layouts need more than a straight lay. The rest of this guide shows how to handle odd shapes, which waste figure to use, and a full worked example.
What you need
- A tape measure, ideally 25 feet or longer.
- Paper to sketch the floor plan. Rough is fine, as long as every wall is labeled.
- The box coverage of the flooring you like, printed on the carton or product page.
Step 1: sketch and split the room
Draw the room from above and mark every wall. Then divide it into shapes you can measure:
- Rectangles and squares: area = length x width.
- Right triangles (a corner cut at an angle): area = base x height / 2.
- Closets, alcoves and bay windows: measure each as its own small rectangle and add it.
An L-shaped room becomes two rectangles. A room with a 45 degree corner becomes a rectangle minus a triangle, or a rectangle plus a triangle, depending on how you draw it. MSI's tile guide gives the same approach for irregular areas: divide the space into separate rectangles, work out each, and add the totals.
Step 2: measure wall to wall
Measure at floor level, from wall to wall, not baseboard to baseboard if the baseboards will come off. If the walls are not quite parallel, measure at both ends and use the longer number. Include doorways where the new floor will run into the opening, and any closet that will get the same floor.
Convert inches to decimal feet before you multiply. 8 inches is 8 / 12 = 0.67 feet, so 12 feet 8 inches is 12.67 feet. Typing 12 feet 8 inches as 12.8 is a common slip that adds error.
Step 3: add a waste allowance
You will lose material to cuts at walls, around door frames and at the end of each row, plus the occasional damaged piece. The right allowance depends on the product and the layout, so the maker's own figure always comes first. Here is what two flooring makers publish:
| Source | Situation | Extra to order |
|---|---|---|
| Mannington | Floors in general | "a waste factor of 5-15% is added to your order, depending on the product" |
| Alpine Floor | Herringbone | "an additional 10-15% for waste" |
| Alpine Floor | Herringbone in a complex space | up to 20% |
Why do diagonal and patterned layouts cost more? In a straight layout, the offcut from the end of one row can often start the next. When pieces run at an angle to the walls, almost every piece that meets a wall is cut on a slant, and many of those offcuts are the wrong shape to use elsewhere. Herringbone and chevron have the same problem at every edge.
Small rooms and rooms with many corners also waste more than one big rectangle, because the share of pieces that need cutting is higher. If your room is chopped up, lean toward the top of the maker's range.
Step 4: convert to boxes
Divide the total with waste by the square feet per box and round up. Never round down: a shortfall of half a box still means a second trip to the store.
Worked example
An L-shaped living room with a closet:
| Part | Size | Area |
|---|---|---|
| Main area | 14 ft x 12 ft | 168 sq ft |
| Alcove | 6 ft x 4 ft | 24 sq ft |
| Closet | 3 ft x 2 ft | 6 sq ft |
| Total | 198 sq ft |
Suppose the chosen product's carton says it covers 22.5 sq ft.
- Straight layout, 10% waste: 198 x 1.10 = 217.8 sq ft. 217.8 / 22.5 = 9.68, so buy 10 boxes (225 sq ft).
- Herringbone layout, 15% waste: 198 x 1.15 = 227.7 sq ft. 227.7 / 22.5 = 10.12, so buy 11 boxes (247.5 sq ft).
The herringbone layout costs one extra box here. On a bigger floor the gap grows: at 600 sq ft the same two allowances differ by 30 sq ft, about one and a third cartons of this size. If the product's own instructions give a different figure, use theirs.
In metric, multiply square feet by 0.09290304 (the NIST factor for one square foot): 198 sq ft is about 18.4 square meters.
Measuring a triangle corner
Say a 12 ft x 10 ft bedroom has one corner cut off at 45 degrees, and the two short walls of the missing triangle are each 3 ft. The full rectangle is 120 sq ft. The missing triangle is 3 x 3 / 2 = 4.5 sq ft. The floor is 120 minus 4.5 = 115.5 sq ft. Add your waste allowance to that figure. Angled walls mean more angled cuts, so this is a room where the higher end of the range is sensible.
Common mistakes
- Measuring only the longest walls of an L-shape. Multiplying the two longest walls overstates the area by the missing corner.
- Mixing feet and inches. Convert inches to decimal feet first.
- Using a generic waste figure when the maker gives one. The product's own instructions win.
- Applying straight-layout waste to a diagonal or herringbone floor.
- Forgetting closets and doorways that will receive the new floor.
- Rounding boxes down.
- Throwing leftovers away. Mannington recommends keeping extra for future repairs.
Measure every room separately, write the numbers on your sketch, and keep the sketch with your receipt. The flooring calculator below takes your room sizes, waste percentage and box coverage and gives the number of boxes to order.
Work out your flooring: tools.dexaloop.com/flooring-calculator/. Free, no sign-up, and it runs on your device.
Questions
Should I measure under the kitchen cabinets or the toilet?
Measure only the floor that will actually be covered. Whether the new floor runs under cabinets, a vanity or appliances depends on the product and the job, so ask your installer before you finalize the number.
How much extra flooring should I order?
Use the figure in your product's own instructions first. Mannington says a waste factor of 5 to 15% is added depending on the product. For herringbone, flooring maker Alpine Floor suggests 10 to 15% extra, and up to 20% for complex rooms. Patterned and diagonal layouts generally need more than a straight lay.
How do I convert square feet to square meters?
Multiply by 0.09290304, the exact factor NIST lists for one square foot. A 198 square foot room is about 18.4 square meters.
Why round up to a full box rather than buy loose planks?
Flooring is sold by the carton, and a part box is not usually available. Divide the area with waste by the coverage printed on the box and round up to the next whole number.
Should I keep the leftover boxes?
Yes. Mannington recommends keeping extra material for possible repairs in the future, which also gives you a match if a plank is damaged later.
Sources
- Mannington Mills: What to expect from your floor installation
- MSI Surfaces: How much wall tile do I need? A guide to DIY backsplashes
- Alpine Floor: How much extra herringbone flooring do you need? A waste calculation guide
- NIST Handbook 44, Appendix C: General tables of units of measurement
This guide is general information, not legal, tax or financial advice. Rules change; check the official source for your own case. Found a mistake? Email support@dexaloop.com.