What this calculator does
Working out a room’s area in square metres is the starting point for flooring, tiling, turf or paint quotes, and for a plain rectangular room the square metre calculation is just length times width. Real rooms are not always a clean rectangle, though, and an alcove, bay or step in one wall means a second section needs adding on top of the main one.
This calculator handles both cases. Enter the main room’s length and width in metres for a straightforward total, or add a second rectangular section as an alcove to get the combined area of an L-shaped room, with the total also converted to square feet and square yards.
The formula
Area of a rectangle is simply length × width, in metres, giving a result in square metres directly. For an L-shaped room, the main section and the alcove section are each treated as their own rectangle and their two areas are added together, since the alcove floor space is separate from, not overlapping, the main room.
| Term | Meaning |
|---|---|
| Main room | The primary rectangular section of the room, entered as its length and width. |
| Alcove | A second rectangular section, such as a bay window recess or step in the wall, added to the main room’s area to cover an L-shaped floor plan. |
| m² | Square metres, the standard metric unit for floor area. |
The inputs explained
| Field | What to enter |
|---|---|
| Room length (m) | The length of the main room, in metres. |
| Room width (m) | The width of the main room, in metres. |
| Alcove length (0 if none) (m) | The length of a second, alcove section, in metres. Leave at 0 along with the width below if the room is a plain rectangle. |
| Alcove width (0 if none) (m) | The width of the alcove section, in metres. Leave at 0 along with the length above if there is no alcove. |
When to use it
A simple rectangular room
A bedroom, lounge or straightforward rectangular space needs just the two main measurements, length and width, leaving the alcove fields at 0 for a plain square metre calculation.
An L-shaped living or kitchen area
An L-shaped kitchen-diner or lounge with a step in the floor plan is entered as a main rectangle plus a second alcove rectangle, and the total area covers both sections together.
Comparing a quote priced per square metre
A flooring, carpet or tiling quote priced per square metre needs the actual floor area first; this gives that figure directly, in square metres, square feet or square yards depending on how the quote is presented.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How does total area change as a rectangular room gets longer?
A fixed room width of 4 m, across a range of room lengths, with no alcove section.
| Room length | Total area | In square feet |
|---|---|---|
| 3 m | 12.000 m² | 129.17 ft² |
| 4 m | 16.000 m² | 172.22 ft² |
| 5 m | 20.000 m² | 215.28 ft² |
| 6 m | 24.000 m² | 258.33 ft² |
| 8 m | 32.000 m² | 344.44 ft² |
Adding an alcove to an L-shaped room
A main room of 5 m by 4 m, with an alcove section 2 m long, across a range of alcove widths.
| Alcove width | Total area | Alcove area |
|---|---|---|
| 1 m | 22.000 m² | 2.000 m² |
| 2 m | 24.000 m² | 4.000 m² |
| 3 m | 26.000 m² | 6.000 m² |
| 4 m | 28.000 m² | 8.000 m² |
| 5 m | 30.000 m² | 10.000 m² |
Questions
How do you work out square metre calculation for a room?
Multiply the room’s length by its width, both measured in metres, to get the area directly in square metres. For an oddly shaped room, split it into rectangular sections, work out each one’s area, then add them together.
How do you calculate square metres for an L-shaped room?
Split the L-shape into two rectangles, a main section and an alcove, measure the length and width of each separately, and add the two areas together for the total.
What is the sq metre calculator conversion to square feet?
Multiply the area in square metres by 10.7639 to get square feet, or by 1.19599 to get square yards, both shown alongside the main square-metre total here.
Does it matter which side is called length and which is called width?
No. Length times width gives the same area as width times length, since multiplication does not depend on the order, so either side can be entered into either field.
For boxes of tiles or flooring needed once the area is known, including a wastage allowance, see the flooring & tiles calculator. For a single rectangle’s area, perimeter and diagonal together, see the rectangle & square calculator.