Flooring is sold by the box, each covering a set number of square feet (often 18–30 ft²). Add waste for cuts at walls and doorways: about 5–10% for straight layouts, 15% for diagonal and 20% for herringbone. Keep a spare box for repairs – dye lots change between batches.
How to use the Flooring Calculator
- Room length
- Room width
- Layout
- Coverage per box
- Flooring price
- Underlayment price
- Installation price
Results update as you type, and every field accepts the units shown in its menu.
How it works
Enter the room length and width, choose the layout, the coverage per box and prices for flooring, underlayment and installation.
Tips for an accurate estimate
- Take measurements at floor level and at the ceiling – walls and rooms are often slightly out of square.
- Use the manufacturer’s coverage, spacing and installation data when it differs from the typical values here.
- Keep a little extra of every finish material for touch-ups and repairs later.
- Check local building codes and permits before structural, electrical, plumbing or gas work.
Common mistakes to avoid
- Sizing heating or cooling equipment by area alone when insulation, windows and climate make a big difference.
- Buying too little paint, stain or flooring and ending up with mismatched batches.
- Overlooking the extra material for steps, railings, gables and trim.
Inputs explained
| Field | What to enter |
|---|---|
| Room length | Units: ft, m, in, yd, cm |
| Room width | Units: ft, m, in, yd, cm |
| Layout | Choose one: Straight – 10%, Straight, few cuts – 5%, Diagonal – 15%, Herringbone / chevron – 20% |
| Coverage per box | Units: ft², m², yd², acre |
| Flooring price | Units: /ft², /m², /yd² |
| Underlayment price | Units: /ft², /m², /yd² |
| Installation price | Units: /ft², /m², /yd² |
What each result means
- Floor area = [Room length]×[Room width]
- Area to buy = [Floor area]×(1 + [Layout]÷100)
- Boxes = ceil([Area to buy]÷[Coverage per box] – 0.000001)
- Flooring cost = [Boxes]×[Coverage per box]×[Flooring price]
- Underlayment and installation = [Floor area]×([Underlayment price] + [Installation price])
- Total cost = [Flooring cost] + [Underlayment and installation]
Example values
How the main result changes when Room length changes and everything else stays at the example values above:
| Room length (ft) | Boxes |
|---|---|
| 7.5 | 5 |
| 11.25 | 8 |
| 15 | 10 |
| 18.75 | 13 |
| 22.5 | 15 |
| 30 | 20 |
Formula
Area to buy = L × W × (1 + waste)Boxes = ceil(area to buy ÷ coverage per box)Cost = boxes × coverage × price + area × (underlayment + installation)Worked example
Inputs — Room length: 15 ft; Room width: 12 ft; Layout: Straight – 10%; Coverage per box: 20 ft²; Flooring price: $3.5 /ft²; Underlayment price: $0.5 /ft²; Installation price: $2.5 /ft².
Results — Floor area = 180 ft²; Area to buy = 198 ft²; Boxes = 10; Flooring cost = $700.00; Underlayment and installation = $540.00; Total cost = $1,240.00.
Frequently asked questions
How much flooring do I need for a 12 × 15 room?
180 ft² plus 10% = 198 ft², or 10 boxes of 20 ft².
How much extra flooring should I buy?
5–10% for straight installs, 15% for diagonal, 20% for herringbone.
Do I need underlayment?
Most floating laminate and vinyl floors need a foam or cork underlayment unless it is pre-attached.
What formula does the Flooring Calculator use?
Area to buy = L × W × (1 + waste).