How much carpet do I need? A table by room size
A 3 × 4 m room (9.8 × 13.1 ft) has 12 m² of floor and needs one unjoined piece of carpet 5 m wide × 3.1 m long (15.5 m²), which is 3.1 linear metres from a 5 m roll, and 1 roll or pack of underlay of 15.07 m² each (15.07 m²). In the table's words: 3.1 m (15.5 m²) off the 5 m roll, or 4.1 m (16.4 m²) off a 4 m roll, with 1 roll or pack of 15.07 m² of underlay. The roll width, the trimming allowance and the underlay pack are generic example figures, not a product’s: check the roll width, the pile direction and any joins with the shop or fitter.
| Room | In feet | Floor area | From a 4 m roll | From a 5 m roll | Underlay | Your room |
|---|---|---|---|---|---|---|
| 2 × 2 m | 6.6 × 6.6 ft | 4 m² | 2.1 m (8.4 m²) | 2.1 m (10.5 m²) | 1 roll or pack of 15.07 m² | Open 2 × 2 m in the planner |
| 2.5 × 3 m | 8.2 × 9.8 ft | 7.5 m² | 2.6 m (10.4 m²) | 2.6 m (13 m²) | 1 roll or pack of 15.07 m² | Open 2.5 × 3 m in the planner |
| 3 × 3 m | 9.8 × 9.8 ft | 9 m² | 3.1 m (12.4 m²) | 3.1 m (15.5 m²) | 1 roll or pack of 15.07 m² | Open 3 × 3 m in the planner |
| 3 × 3.5 m | 9.8 × 11.5 ft | 10.5 m² | 3.1 m (12.4 m²) | 3.1 m (15.5 m²) | 1 roll or pack of 15.07 m² | Open 3 × 3.5 m in the planner |
| 3 × 4 m | 9.8 × 13.1 ft | 12 m² | 4.1 m (16.4 m²) | 3.1 m (15.5 m²) | 1 roll or pack of 15.07 m² | Open 3 × 4 m in the planner |
| 3.5 × 4 m | 11.5 × 13.1 ft | 14 m² | 4.1 m (16.4 m²) | 3.6 m (18 m²) | 1 roll or pack of 15.07 m² | Open 3.5 × 4 m in the planner |
| 4 × 4 m | 13.1 × 13.1 ft | 16 m² | Too wide for one piece | 4.1 m (20.5 m²) | 2 rolls or packs of 15.07 m² | Open 4 × 4 m in the planner |
| 4 × 5 m | 13.1 × 16.4 ft | 20 m² | Too wide for one piece | 5.1 m (25.5 m²) | 2 rolls or packs of 15.07 m² | Open 4 × 5 m in the planner |
| 4.5 × 4.5 m | 14.8 × 14.8 ft | 20.25 m² | Too wide for one piece | 4.6 m (23 m²) | 2 rolls or packs of 15.07 m² | Open 4.5 × 4.5 m in the planner |
| 4.5 × 5 m | 14.8 × 16.4 ft | 22.5 m² | Too wide for one piece | 5.1 m (25.5 m²) | 2 rolls or packs of 15.07 m² | Open 4.5 × 5 m in the planner |
Each row is the planner’s answer for that room, worked out when this page was built. The link at the end of a row opens the planner with that room filled in, to change the measurements and the product figures.
The planner adds 0.1 m to each measurement for trimming, and cuts one piece with no join. So a 4 m roll covers a room up to 3.9 m across. It is too narrow for the 4 × 4 m room, the 4 × 5 m room, the 4.5 × 4.5 m room and the 4.5 × 5 m room. A room more than 4.9 m across both ways needs a join, which the planner does not plan.
The figure is the length to ask for, in metres off the roll, with the square metres of that piece in brackets. A carpet is sold by the roll width, so the piece is always wider than the room unless the room is exactly as wide as the roll. Which way the pile or the pattern must run can change the cut: the carpet calculator asks.
The roll widths, the allowance and the underlay pack are the planner’s generic examples, not a product’s. How much carpet do I need? works through a room.
What the table assumes
Each room is a rectangle, with one door 0.762 m × 1.981 m.
- 1 door entered for the threshold-bar count. Openings are not taken off the floor.
- Carpet: one rectangular room, one unjoined piece from a 5 m roll. The 0.1 m trimming allowance is added to each room measurement. Check the pile or pattern direction before ordering.
- The carpet cut is rounded once up to the shop step; underlay is rounded once up to whole packs. Working uses unrounded figures.
- Carpet and Carpet underlay use generic example figures, not the figures of any product. Enter the roll, shop and underlay figures for a closer answer.
How this table was made
It was worked out when this page was built, by the same room planner and formulas as the editable list: each row is one room sent through the planner. The room sizes are round examples. Product coverage, pack and allowance figures are the planner’s labelled generic examples, not figures for a product.
AI tools drafted the page and automated tests compare every cell with the planner. It has not been checked by a tradesperson or anyone outside the build. No price is shown or used.
Before you use it
Measure your own room, its doors and its windows. Check the figures against the room, and follow each product's own instructions: they decide coverage, coats and preparation.
Built and checked with AI tools, not yet by a tradesperson or anyone outside the build. Estimates are arithmetic on your measurements and the figures shown with them: follow each product's own instructions.