How to use the carpet calculator
- Add each room with its length and width, measured at the widest points and into doorways.
- Choose the roll width — 12 ft is most common in the US; 4 m and 5 m in Europe.
- Keep about 3 in (8 cm) of trim on each end of every cut.
- Optionally add the carpet price and the padding and installation price for a cost estimate.
How the calculator works
Floor area = Length × Width Strips needed = Width across the roll ÷ Roll width (rounded up) Carpet to buy = Strips × Roll width × (Run length + 2 × trim) Square yards = Square feet ÷ 9 The roll direction is chosen to use the least carpet.
Worked examples
- 15 × 12 ft bedroom: one 12 ft strip, 15 ft long = 180 ft² = 20 yd². With 3 in trim on each end, 186 ft² (20.7 yd²).
- 16 × 14 ft living room: the floor is 224 ft², but a 12 ft roll needs two strips 14 ft long = 336 ft² (37.3 yd²). An installer may fill the 2 ft gap from another room’s offcut to reduce this.
Common room sizes
| Room | Floor area | Carpet from a 12 ft roll |
|---|---|---|
| 10 × 10 ft | 100 ft² (11.1 yd²) | 120 ft² (13.3 yd²) |
| 12 × 12 ft | 144 ft² (16 yd²) | 144 ft² (16 yd²) |
| 12 × 15 ft | 180 ft² (20 yd²) | 180 ft² (20 yd²) |
| 12 × 18 ft | 216 ft² (24 yd²) | 216 ft² (24 yd²) |
| 14 × 16 ft | 224 ft² (24.9 yd²) | 336 ft² (37.3 yd²) |
| 15 × 20 ft | 300 ft² (33.3 yd²) | 360 ft² (40 yd²) on 12 ft, 300 ft² on 15 ft |
Rooms up to 12 ft wide fit a 12 ft roll with almost no waste. Wider rooms create waste — a 15 ft roll can be cheaper overall even at a higher price per yard.
Measuring tips
- Measure into doorways to the middle of the door threshold, where the carpet meets the next floor.
- Include closets as part of the room or as separate small rooms.
- Stairs: allow about 1 yd² per standard step (tread plus riser), more for bullnose or winder stairs.
- Pattern repeat: patterned carpet needs extra length to match seams — ask the retailer.
- Let the installer measure before ordering: they know how to place seams and reuse offcuts.
Choosing carpet and padding
Nylon is the most durable and resilient carpet fibre and suits busy homes, polyester is soft and stain-resistant at a lower price, and wool is natural and long-lasting but costs more. Padding makes a big difference to comfort and wear: for most residential carpet a 7/16 in, 6–8 lb density rebond pad is common, while low-profile Berbers need a thinner, firmer pad. Check the carpet warranty, which often specifies the pad.