Quick answer: Measure each room’s square footage, add them up, then add a waste allowance: about 10% for a standard straight layout and 15–20% for diagonal or herringbone. Divide by the square feet in a box and round up.
Buying flooring is a balance. Order too little and you risk a second batch that doesn’t quite match; order too much and you’ve paid for boxes that sit in the garage. Here’s how to land on the right number.
Step 1: Measure each room’s square footage
Measure inside the room, wall to wall, at floor level. Include closets and the space under appliances or vanities if the flooring will run underneath. For rectangles, multiply length × width. For L-shaped or angled rooms, split them up (see irregular room square footage) or use the square footage calculator.
Step 2: Add the rooms together
| Room | Size | Sq ft |
|---|---|---|
| Living room (L-shape) | (20 × 15) − (8 × 6) | 252 |
| Hallway | 10 × 3.5 | 35 |
| Closet | 6 × 2.5 | 15 |
| Total | 302 |
Step 3: Add a waste factor
Cuts at walls, damaged pieces and pattern matching all use extra material. Typical allowances:
| Layout / material | Add |
|---|---|
| Straight lay, rectangular room | 5–10% |
| Irregular room, lots of corners | 10–15% |
| Diagonal layout | 10–15% |
| Herringbone or chevron | 15–20% |
| Large-format or patterned tile | 10–15% |
Check the manufacturer’s guidance too. Some products recommend a specific overage.
Example: 302 sq ft × 1.10 = 332.2 sq ft needed.
Step 4: Convert to boxes
Flooring boxes list their coverage in square feet. Divide and always round up.
If a box covers 22.5 sq ft: 332.2 ÷ 22.5 = 14.76 → 15 boxes (337.5 sq ft).
Buy all boxes from the same production lot so color and texture match, and keep one spare box for future repairs.
Carpet: convert to square yards
Carpet is often priced per square yard. Divide square feet by 9:
302 sq ft ÷ 9 = 33.56 sq yd, plus 10% = 36.9 sq yd.
Broadloom carpet usually comes in 12 ft or 15 ft widths, so seam placement can add more waste than the percentage suggests. Your installer will plan the layout.
Tile: count the pieces
Divide the area of the floor by the area of one tile, in the same units.
- 12 × 12 in tile = 1 sq ft each → 332 tiles for 332.2 sq ft
- 12 × 24 in tile = 2 sq ft each → 166.1 → 167 tiles
- 24 × 24 in tile = 4 sq ft each → 83.05 → 84 tiles
Then round up to full boxes.
Step 5: Estimate the cost
Material cost = Square feet to buy × Price per sq ft
At $3.79/sq ft for the 15 boxes (337.5 sq ft): 337.5 × 3.79 = $1,279.13.
Don’t forget the extras that are also priced by area or length:
- Underlayment: usually priced per square foot, at roughly the floor area.
- Baseboard and quarter-round: priced per linear foot. Use the room’s perimeter minus doorways. For the L-shaped living room, the perimeter is 2 × (20 + 15) = 70 ft; minus a 3 ft doorway = 67 linear ft.
- Transitions and thresholds: one per doorway where the floor changes.
- Installation: often quoted per square foot, so multiply by the area installed (not the area purchased).
Common flooring estimate mistakes
- Measuring only the “open” floor and forgetting closets, pantry or the space under the dishwasher.
- Applying waste to each room and the total. Add it once, to the total.
- Rounding boxes down. You can usually return a sealed spare box, but you can’t always match a second order.
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