It can be difficult for homeowners to get room sizes right, and work out if a space 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. Here, we look at how to get it right for your building or renovation project.

Overall House Size

Many homeowners think that their new house needs to be at least 232m² (2,500ft²) but ideally 282m² (3,000ft²). When you consider 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.

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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.

(MORE: The complete guide to self build)

Working Out House and Room Sizes

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% of the final sum.

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.

What Size Should a Kitchen Be?

If you fancy a square kitchen with three sides of units/worktops and a central island, then a size of around 4.8 x 4.2m (20.16m²) is ideal. 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.

Getting room sizes in a kitchen is important as you'll be using this space the most. This open plan kitchen works perfectly for family life

Getting room sizes right in a kitchen is important as you’ll be using this space the most. The open plan kitchen in this stylish modern home works perfectly for family life

A breakfast area should ideally be somewhere in the region of 3 x 3m (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 add around 1m to each of these dimensions as a minimum.

A space for a breakfast and sitting area which is perhaps 4.5 x 4m (18m²) would be considered a good minimum, and it would work well up to 5 x 6m (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

How Much Space Do You Need in a 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, a minimum of 1m of circulation space around the table is needed, but ideally more like 2m, certainly on at least two sides.

This dining room size is perfect for accommodating a large table as well as circulation space

Whether you have a separate dining room or an open plan arrangement, such as in this budget kitchen extension, make sure your room size is large enough to comfortably house a dining table, chairs and circulation space

How to Get Living Room Sizes Right

An ideal size for the formal living room is often dictated by how you want to plan the sitting locations. Typically, homeowners will ask for three sofas in a ‘courtyard’ arrangement facing the fireplace. It will also depend whether you want the furniture to be within the room or up against the wall.

Living room sizes can be hard to get right with striking a balance between cosy and inviting as well as providing room for entertaining. This oak frame self build offers enough space for lounging and relaxing

Living room sizes can be hard to get right with striking a balance between cosy and inviting as well as providing room for entertaining. This oak frame barn-style self build offers room for lounging and relaxing, with generous circulation space

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

Suggested size

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

What Should a Utility Room Size Be?

Close to the kitchen should be the utility room which can work fairly well at around 1.8 x 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.

Utility room sizes should be able to accommodate enough storage spae for the household as well as washer and dryers

This utility room by Charlie Kingham Handmade Bespoke Kitchens comfortably houses storage space  to hold household wares, a space to unload muddy boots before entering the house and a washer and dryer

Where you want to create additional storage for boots and coats, and even space for a pet’s bed, then an ideal utility room size would be more like 2.4 x 3m (7.2m²). 

Suggested size

  • 4.32–7.2m²

How Big Should the Bedroom Be?

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 (1.5 x 2m) or a super king size bed (1.8 x 2m) plus any wardrobe space.

An optimum size for a master bedroom would be around 4 x 4m up to around 4.5 x 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 x 1.8m as a minimum beyond the bedroom itself.

This master bedroom in a beautiful New England-style remodel boasts a comfortable room size which feels even more generous thanks to the vaulted ceiling

This master bedroom in a beautiful New England-style remodel boasts a comfortable room size which feels even more generous thanks to the vaulted ceiling

A second bedroom, typically for guests, can be somewhat less as it will feature either a double bed (1.35 x 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 3.4 x 3m (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 x 1.9m or small double bed at 1.2 x 1.9m and perhaps a small wardrobe and dressing table. A typical minimum room size here would be approximately 3 x 2m (6m²) but ideally more like 3.6 x 2.6m (9.36m²) up to 4 x 3m (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

How Much Space Do You Need in a Bathroom?

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

This bathroom boasts a generous room size with space for a separate freestanding bath and shower cubicle

This bathroom in a sloping site self build boasts a generous room size with space for a separate freestanding bath and shower cubicle

Suggested sizes

  • En suites 2.88–4.4m²
  • Family bathroom 7.2–9m²

Planning Room Sizes: Why 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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