It’s difficult for homeowners to work out if a room is ‘too big’ or ‘too small’. To an extent the answer is subjective, but there is a science to space planning that ensures rooms work effectively without losing their sense of intimacy.

Getting room and overall house sizes perfectly suited to you is a vital part of the overall design process. Over the next few pages we explain how to get it right.

Budget is Key

When considering the spatial requirements of your project, firstly make sure you set your budget out clearly and convey this in as much detail as you can to your architect or designer. It will be their remit to ensure they design a house you can afford to build and finish.

As an industry, we use various benchmark figures for initial calculations based on square metre prices which are useful as an initial check to see if the overall aims for the project can be realised (check out our Build Cost Calculator). The various multiples will vary based on how you intend to build the project.

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Overall House Size

I have lost count of how many times I have sat down with clients and they have said that their new house needs to be at least 232m² (2,500ft²) but ideally 282m² (3,000ft²). When you bear in mind that the approximate national UK average for a three bedroom/two bathroom dwelling is around 88–100m² and an average four bedroom/three bathroom dwelling is approximately 100–140m², the perceived ideal starting point is a fair bit larger.

It is often the case that a self built home is going to be larger than a developer built home, as this is your opportunity to create a bespoke home and you will strive to achieve as much as you can. However, it is worth reassessing size and space as you work through the various design phases. If it turns out that you can build a slightly smaller house with a higher specification and guaranteed completion, then this would be a worthy consideration — particularly as smaller houses tend to be cheaper to run.

You should also clarify from the outset with your architect or designer, package company, contractors and lending partner, what ‘size’ you’re measuring. You can calculate your project on the:

  • gross external footprint, measuring all the space including the thickness of the external walls
  • or net internal footprint (excluding the thickness of the external walls) as this can make a huge difference of between 10–12 percent of the final sum.

From my experience, professionals such as estate agents and contractors working internally will be in the mindset of expressing the project on net internal, whereas main contractors and package companies will work on the gross external, as this is ultimately what they are supplying.

Living Room

An ideal size for the formal living room is often dictated on how you want to plan the sitting locations. Typically, my clients will ask for three sofas in a ‘courtyard’ arrangement facing the fireplace. In addition to this, however, they like the furniture to be within the room and not up against the wall.

Living room in a large self build classical style self build in Cheshire

On this basis, a living room/space of around 7.6×6.1m (46.36m²) seems to work as an optimum when I am designing for clients. This is based on a ‘master’ sofa of a typical size of 2.4×0.9m and two secondary sofas measuring approximately 2×0.9m.

Suggested size: Up to 46.36m² (based on a courtyard arrangement of three sofas, including a ‘master’ sofa)


If you fancy a square kitchen with three sides of units/worktops and a central island, then I would suggest an ideal size of around 4.8×4.2m (20.16m²). This is calculated across the width as 60cm unit/1.2m passing space/1.2m central island/1.2m passing space/60cm unit, which in turn equates to 4.8m.

The depth of the space can be slightly less at 4.2m, as the kitchen is more often than not open plan to a breakfast, dining or sitting area. Multiples of kitchen units are typically 60cm or 1.2m, so it makes sense to design your kitchen based on these standard sizes.

Contemporary country style kitchen with island and shaker style units in an oak frame home

A breakfast area should ideally be somewhere in the region of 3x3m (9m²) for a six-person table and a side piece of furniture such as a dresser. If you want this part of the house to feature a sofa then I would add around 1m to each of these dimensions as a minimum.

A space for a breakfast and sitting area which is perhaps 4.5x4m (18m²) would be considered a good minimum, and it would work well up to 5x6m (30m²), however be aware that anything greater than this could lose the relaxed feel of the space and potentially feel too large and impersonal for family gatherings.

Suggested sizes:
Kitchen 20.16m²
Breakfast area 9m²
Breakfast area with seating 18–30m²

Dining Room

If you plan on a separate dining room, this is often dictated by an existing table you might have. In addition to the table dimensions, I would suggest a minimum of 1m of circulation space around the table but ideally more like 2m, certainly on at least two sides.

Dining room opening out onto a terrace in a hillside home


Close to the kitchen should be the utility room which can work fairly well at around 1.8×2.4m (4.32m²) as a minimum. A 1.8m width will allow the inclusion of a 60cm-deep unit/worktop with a walk-past space of 1.2m and the 2.4m length will allow four 60cm base units to include space for a washing machine, tumbler dryer and storage space. An ideal size would be more like 2.4x3m (7.2m²), as this will allow greater storage options such as boots and coats, and also maybe space for a pet’s bed.

Suggested size: 4.32–7.2m²

Country style utility with butler sink in an oak frame home


Bedrooms are dictated by the size of the bed and also the functionality of the bedroom itself. The master bedroom is likely to feature either a king size bed (1.5x2m) or a super king size bed (1.8x2m) plus any wardrobe space. Therefore, an optimum size for a master bedroom would be around 4x4m up to around 4.5×4.5m (20.25m²). This would allow enough space around the bed and also room for a sitting and/or dressing area. If you plan on having a dressing room separate from the bedroom then I would allow a space of around 1.8×1.8m as a minimum beyond the bedroom itself.

Oak frame home master bedroom with vaulted ceiling

A second bedroom, typically for guests, can be somewhat less as it will feature either a double bed (1.35×1.9m) or a king size and doesn’t necessarily need lots of wardrobe/dressing space. Such a room can work at somewhere in the region of 3.4x3m (10.2m²). The additional bedrooms are typically for the children within the family and this is where the issue of functionality comes into the design process. For younger children, the bedroom will need to incorporate only a single bed at 0.90×1.9m or small double bed at 1.2×1.9m and perhaps a small wardrobe and dressing table. A typical minimum for such a room would be approximately 3x2m (6m²) but ideally more like 3.6×2.6m (9.36m²) up to 4x3m (12m²) as this will allow for the inclusion of desk space for their homework projects as they get older, and also they will need more storage. Children are staying at home for longer nowadays, too, so your layout should be future-proofed in this respect.

Suggested sizes:
Master bedroom 20.25m²
Second/guest bedrooms 10.2m²
Children’s bedrooms 6–12m²


En suites with a shower, WC and basin should generally be at least 1.8×1.6m (2.88m²), up to an ideal of approximately 2×2.2m (4.4m²) and a family bathroom featuring a shower, bath, WC and basin should be around 2.4x3m (7.2m²) up to an ideal of 3x3m (9m²).

Suggested sizes:
En suites 2.88–4.4m²
Family bathroom 7.2–9m²

Sleek modern bathroom with teal walls and a room divide

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