Area, Property and Floor Space Measurement
Quick answer: Area is length multiplied by width. Measure a rectangular room in metres and multiply the two figures to get square metres (m²); one square metre is about 10.76 square feet. UK property listings, energy certificates and planning documents use square metres, while many people still think in square feet and acres.
This section explains how to measure the area of rooms, homes and plots of land, how to convert between metric and imperial units, and what the UK’s minimum room size rules say.
Area measurements decide how much flooring, paint or turf you buy, how a home is described when it is sold or let, and whether a bedroom is big enough to be used as one under licensing rules. The maths is simple, but small slips, such as measuring in centimetres and reporting in metres, or converting square metres with a length factor, can make a figure wildly wrong.
For quick conversions between square metres, square feet, acres and hectares, use the area converter. The units of measurement guide explains how square units relate to the metric and imperial length units they come from.
How do you work out the area of a room?
Measure the length and width of the floor in metres and multiply them: a room 4 m long and 3.5 m wide has an area of 14 m². Measure wall to wall at floor level, ignoring skirting boards, and take the measurement in two or three places if the walls are not parallel. Use the larger figures when buying flooring and the smaller ones when checking whether furniture will fit.
Room area calculator
m long m wide= m² ( ft²)For an L-shaped or irregular room, split the floor into rectangles, work out each area separately and add them together, as the diagram shows. Bay windows and chimney breasts can be handled the same way: add the area of a bay as an extra rectangle or triangle, and subtract the footprint of a chimney breast.
How many square feet are in a square metre?
One square metre is 10.764 square feet, and one square foot is 0.0929 square metres. The factor is the square of the length factor: a metre is 3.2808 feet, and 3.2808 × 3.2808 = 10.764. Using 3.28 instead of 10.76 is one of the most common mistakes when converting floor areas.
| Square metres | Square feet |
|---|---|
| 1 m² | 10.76 ft² |
| 5 m² | 53.82 ft² |
| 10 m² | 107.64 ft² |
| 15 m² | 161.46 ft² |
| 20 m² | 215.28 ft² |
| 25 m² | 269.10 ft² |
| 50 m² | 538.20 ft² |
| 75 m² | 807.29 ft² |
| 100 m² | 1,076.39 ft² |
| 150 m² | 1,614.59 ft² |
| 200 m² | 2,152.78 ft² |
| Square feet | Square metres |
|---|---|
| 100 ft² | 9.29 m² |
| 250 ft² | 23.23 m² |
| 500 ft² | 46.45 m² |
| 750 ft² | 69.68 m² |
| 1,000 ft² | 92.90 m² |
| 1,500 ft² | 139.35 m² |
| 2,000 ft² | 185.81 m² |
How is floor area measured when a home is sold or let?
UK energy performance certificates state a total floor area in square metres, and estate agents’ floor plans usually give an internal area in square metres and square feet. Professional measurement follows guidance from the Royal Institution of Chartered Surveyors (RICS), which defines measures such as gross internal area, the floor area measured to the inside face of the external walls.
Figures from different sources can differ because they include or exclude different spaces, such as garages, conservatories, stairwells and rooms with low ceilings. If size matters to a purchase, ask how the area was measured, or measure the rooms yourself. You can look up the floor area on a home’s certificate using the GOV.UK energy certificate service.
What is the minimum size for a bedroom in the UK?
In England, a room in a licensed house in multiple occupation (HMO) must be at least 6.51 m² to be used as a bedroom by one person over 10, and at least 10.22 m² for two people over 10. A room used by one child under 10 must be at least 4.64 m². Any floor area where the ceiling is lower than 1.5 m does not count towards these figures.
New homes are a different matter. Where a local planning authority has adopted the Nationally Described Space Standard, a single bedroom must be at least 7.5 m² and 2.15 m wide, and a double or twin bedroom at least 11.5 m², with the main one at least 2.75 m wide and any others at least 2.55 m wide. The same standard sets minimum overall floor areas for whole homes.
| Rule | Room or home | Minimum |
|---|---|---|
| HMO licence condition (England) | Bedroom, one person over 10 | 6.51 m² |
| HMO licence condition (England) | Bedroom, two people over 10 | 10.22 m² |
| HMO licence condition (England) | Bedroom, one child under 10 | 4.64 m² |
| Nationally Described Space Standard | Single bedroom | 7.5 m², at least 2.15 m wide |
| Nationally Described Space Standard | Double or twin bedroom | 11.5 m², at least 2.55 m wide (main bedroom 2.75 m) |
| Nationally Described Space Standard | 1 bedroom, 2 person flat on one storey | 50 m² gross internal area |
| Nationally Described Space Standard | 2 bedroom, 4 person home on one storey | 70 m² gross internal area |
These rules apply in England and may be changed or supplemented by local councils, and different rules apply in Scotland, Wales and Northern Ireland. Check with your council’s private housing or planning team before relying on a figure.
How big is an acre or a hectare?
An acre is 4,046.86 m², about the area of a square 63.6 m on each side, and a hectare is 10,000 m², a square 100 m by 100 m. One hectare is 2.471 acres, and one acre is 0.4047 hectares. Hectares are standard in official statistics and planning documents, but acres remain common in everyday conversation, estate agents’ particulars and farming.
| Unit | Square metres | Hectares | Acres |
|---|---|---|---|
| 1 square metre | 1 | 0.0001 | 0.000247 |
| 1 are (100 m²) | 100 | 0.01 | 0.0247 |
| 1 acre | 4,046.86 | 0.4047 | 1 |
| 1 hectare | 10,000 | 1 | 2.471 |
| 1 square kilometre | 1,000,000 | 100 | 247.1 |
Gardens and outdoor spaces use the same methods as rooms, with triangles (half the base times the height) and circles (π times the radius squared) for awkward shapes. The garden measuring guides cover lawns, patios and raised beds in more detail.
What mistakes should you avoid when measuring area?
- Mixing centimetres and metres. 400 cm × 350 cm is 140,000 cm², which is 14 m²; one square metre is 10,000 cm², not 100.
- Converting with a length factor. Multiply square metres by 10.764, not 3.28, to get square feet.
- Forgetting wastage. Flooring and tiles need extra for cutting and pattern matching; follow the maker’s recommended allowance.
- Measuring to the wrong surface. Room areas are measured wall to wall inside; building footprints are measured outside.
- Counting low-ceiling space as usable. Under the HMO rules, floor below 1.5 m ceiling height does not count.
Area and property guides in this section
- Area converter: square metres, square feet, acres, hectares and more.
- How to measure stairs for carpet: treads, risers and nosings.
- How to measure for wallpaper: wall area and the number of rolls.
- How to measure windows for replacement: openings measured at several points.
Latest area and property guides
Related sections
For measuring individual fittings and furnishings, see the home and DIY measuring guides; for tapes and laser measures, see measuring tools and how to use them. The units of measurement guide covers the wider metric and imperial system.
Frequently asked questions
How do I calculate the square metres of a room?
Measure the length and width in metres and multiply them. A room 5 m by 4 m is 20 m². For an L-shaped room, split it into rectangles and add the areas.
How many square feet is 1 square metre?
One square metre is 10.764 square feet. To go the other way, multiply square feet by 0.0929 to get square metres.
What is the smallest legal bedroom size in the UK?
For licensed HMOs in England, a bedroom for one person over 10 must be at least 6.51 m², or 4.64 m² for a child under 10. New homes built to the Nationally Described Space Standard need single bedrooms of at least 7.5 m².
How many square metres is an acre?
An acre is 4,046.86 square metres, or about 0.405 hectares. A hectare is 10,000 square metres, or about 2.471 acres.
Why does the floor area on my EPC differ from the estate agent’s figure?
Different measurements include or exclude different spaces, such as garages, conservatories and areas with low ceilings, and are measured to different surfaces. Ask how each figure was measured.
Sources
- The Licensing of Houses in Multiple Occupation (Mandatory Conditions of Licences) (England) Regulations 2018, legislation.gov.uk
- Technical housing standards: nationally described space standard, GOV.UK
- Find an energy certificate, GOV.UK
- Royal Institution of Chartered Surveyors (RICS): property measurement standards
- National Physical Laboratory: SI units and definitions