A bedroom is one of the few rooms whose size is decided almost entirely by one object. The bed is fixed, it cannot be angled, and the space around it is not decoration. Work outward from the bed and the room sizes itself.
The sizes
| Bedroom | Area | Worked size | What it buys |
|---|---|---|---|
| Single, minimum | 7 m² | 2.6 × 2.7 m | A single bed, a narrow wardrobe and floor to stand in. Nothing else fits. |
| Single, comfortable | 9–10 m² | 3.0 × 3.2 m | Adds a desk, or a chest of drawers and room to open it. |
| Double, minimum | 11.5 m² | 3.0 × 3.8 m | A double bed with access on both sides and a wardrobe wall. |
| Double, comfortable | 12–13 m² | 3.2 × 4.0 m | The figure to design an ordinary bedroom to. |
| Main bedroom | 14–16 m² | 3.6 × 4.0 m | A king bed, two bedside tables, a full wardrobe run and a chair. |
| Main with ensuite | 18–22 m² | 4.0 × 5.0 m | The bedroom above plus 4–6 m² of shower room off it. |
The minimum figures are advisory habitability rules of thumb, not any one country's building code. They sit at the tight end deliberately: a room that fails one of them fails it everywhere, and a room that passes still has to satisfy whatever your local authority requires. Minimum room sizes are set nationally and sometimes locally.
Why the width fails before the area does
Area is the number people quote and width is the number that decides whether the room works. A 12 m² bedroom can be 3.2 × 3.75 m, which is comfortable, or 2.4 × 5.0 m, which is a corridor with a bed at one end. Both report 12 m².
The clear width to hold onto is 2.0 m as an absolute minimum and 2.4 m for a double: a 1400 mm bed plus 400 mm to get in on one side is 1.8 m, and a bed you can walk round on both sides is 1400 plus 700 twice, which is 2.8 m. Below 2.4 m the bed has to go against a wall, and one person is climbing over the other.
Keep habitable rooms between square and about 1:1.5. Beyond that the far end of the room stops being usable for anything, which is floor you paid for and cannot furnish.
What eats the floor
| Item | Size | Note |
|---|---|---|
| Double bed | 1400 × 2000 mm | A king is 1600–1800 wide, which is 400 mm more room, not 100. |
| Access down one side | 400 mm | The absolute minimum to get into bed. Bedside tables are 400 mm and live in this gap. |
| Access down both sides | 700 mm each | What a bedroom shared by two people actually needs. |
| Wardrobe depth | 600 mm | A hanger is 550 mm across. A 500 mm wardrobe holds coats sideways and nothing else. |
| Standing room at the wardrobe | 550–750 mm | To stand and swing the doors. Sliding doors save this, not the depth. |
| Door swing | The door's own width | A 800 mm door claims 800 mm of clear floor inside the room. |
Add those up for a double bedroom and the arithmetic is unforgiving. Across the room: 1400 for the bed plus 700 on each side is 2.8 m. Down the room: 2000 for the bed, 600 for the wardrobe and 750 to stand at it is 3.35 m. That is 9.4 m² before the door has swung and before anything stands at the foot of the bed, which is why 11.5 m² is a minimum rather than a target.
Four decisions that matter as much as the size
- Do not put the bed head under the window. It means draughts, a window that cannot be opened from the bed and curtains behind your head. A high sill of 1200 mm or more is fine.
- Give the wardrobe a wall the bed does not want. This is the real difference between a 9 m² and a 12 m² bedroom. If the only free wall is the one at the foot of the bed, the room is a single.
- Swing the door against a wall. The leaf should park flat rather than sweeping the room, and its swing needs the door's own width of clear floor inside the room.
- Check the daylight. The old rule of thumb is glazing of at least an eighth of the floor area, so a 14 m² bedroom wants about 1.8 m² of window.
Sizing bedrooms inside a whole house
Bedrooms take roughly 30 to 35 per cent of the net floor area of a family house, all of them together. On an 81 m² net plan that is 24 to 28 m², which is one 13 m² main bedroom and two smaller rooms, or two comfortable doubles.
Do not give every bedroom the same area. Equal bedrooms are a school; a house gives the surplus to the main bedroom and holds the third bedroom near its minimum. And when the total does not fit, drop a bedroom rather than shaving all of them: three rooms at 8, 8 and 8 m² is a worse house than two at 13 and 11. The method is in how to allocate floor area between rooms.