Quick answer: Measure each rectangular section wall to wall, multiply length × width, add the areas together, add 10% for waste (15% or more for diagonal or herringbone layouts) and divide by the coverage on one box. Always round up to whole boxes.
Accurate measurements are the foundation of any flooring project. Order too little and you may not find the same batch again; order too much and you pay for boxes you do not need. Here is the method professional installers use.
What You Need
- A tape measure or laser measure
- Graph paper or a notes app to sketch the room
- A calculator, or our flooring calculator
Step 1: Sketch the Room
Draw a rough floor plan including closets, alcoves, doorways and any built-in units. You do not need to draw to scale; the sketch is just for writing measurements on.
Step 2: Split the Room into Rectangles
Most rooms are one rectangle. L-shaped rooms, rooms with bay windows or open-plan spaces should be split into two or more rectangles. Measure each one separately.
Step 3: Measure Wall to Wall
Measure the length and width of each rectangle at the floor, from wall to wall, not from baseboard to baseboard. Walls are rarely perfectly square, so measure in two or three places and use the largest number. Round up to the next inch or centimeter.
Step 4: Calculate the Area
Area = Length × Width (for each rectangle), then add them together
Example: an L-shaped living room made of a 15 × 12 ft rectangle and an 8 × 6 ft dining nook is 180 + 48 = 228 sq ft.
Step 5: Add a Waste Allowance
| Layout | Waste to add |
|---|---|
| Straight lay, simple room | 5–10% |
| Many corners or closets | 10–15% |
| Diagonal | 15% |
| Herringbone or chevron | 15–20% |
For the L-shaped room with 10% waste: 228 × 1.10 = 250.8 sq ft.
Step 6: Convert to Boxes
Check the coverage printed on the box, then divide and round up. If each box covers 22 sq ft, you need 250.8 ÷ 22 = 11.4, so 12 boxes.
Skip the math: enter each rectangle, your waste allowance and box coverage to get the exact number of boxes and the cost. Open the free Flooring Calculator →
Metric Example
A bedroom 4.2 × 3.5 m is 14.7 m². With 10% waste that is 16.2 m². With packs of 2.13 m², you need 7.6, so 8 packs.
Common Measuring Mistakes
- Forgetting closets, hallways or the space under appliances.
- Measuring to the baseboard instead of the wall.
- Using square yards for carpet but square feet for the box coverage. Keep units the same (1 sq yd = 9 sq ft).
- Not allowing extra for pattern matching on patterned carpet or tile-look vinyl.
Before You Buy
Buy all boxes at once and check that the batch or lot numbers match. Keep one spare box for future repairs. Planning to tile the bathroom too? Our guide on how many tiles you need covers tile layouts and grout.
Frequently Asked Questions
Do I measure to the wall or the baseboard for flooring?
Measure to the wall. The expansion gap at the edge is hidden under the baseboard and is covered by your waste allowance.
How much extra flooring should I buy?
About 10% for a standard straight layout. Use 15% for diagonal layouts or rooms with many corners and up to 20% for herringbone.
How do I measure an L-shaped room for flooring?
Split it into two rectangles, measure and multiply each one, then add the two areas together before adding waste.
Related Guides
- How Many Tiles Do I Need for a Bathroom Floor or Shower?
- How Much Paint Do I Need for a Room? (Chart by Room Size)
- How Many Sheets of Drywall Do I Need for a Room?
Try the free Flooring Calculator or browse all home improvement calculators.