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Key takeaways
- A standard 5 m tape measure is sufficient for most rooms; a 10 m tape covers open-plan spaces.
- Laser distance meters (20–60 EUR) are faster and more accurate than tape for large or irregular rooms.
- Smartphone apps using LiDAR (iPhone 12 Pro and later, some Android devices) can generate a full floor plan in minutes.
- French law (Loi Carrez for sales, surface habitable for rentals) excludes spaces under 1.80 m ceiling height from the legal floor area.
- Always measure length times width for each rectangular zone, then add irregular sections separately.
Why measurement matters
Whether you are a tenant checking the floor area in your lease, a landlord calculating rent for a French property, or simply planning where to put the sofa, accurate measurement matters. An incorrect figure in a lease is not just inconvenient — in France it can have direct legal and financial consequences.
In France, two legal definitions of floor area are relevant. The surface habitable applies to rental contracts under Loi Boutin (2009). The surface Carrez applies to property sales for apartments in co-ownership. Both definitions exclude areas where the ceiling height is below 1.80 m. A sloped roof room is therefore smaller on paper than it looks in person.
This guide covers how to measure accurately using whatever tools you have available, from a basic tape measure to a laser device to a smartphone app.
Choosing your measurement tool
The right tool depends on the accuracy you need, how many rooms you are measuring, and whether you are working alone.
Tape measure
The most accessible option. A 5 m steel tape measure is available from any hardware shop for around 5–10 EUR and is adequate for individual rooms. A 10 m tape is better for open-plan spaces or long corridors. Two people make the job easier: one holds the end against the wall, the other reads the measurement at the opposite wall. For legal measurements such as surface habitable, a tape measure remains the standard tool.
Laser distance meter
A handheld laser device (brands include Bosch, Leica, and Stanley; cost: 20–60 EUR) measures distances by bouncing a laser off the opposite wall. Much faster than tape for large spaces, and accurate to within 1–2 mm. Single-person operation is straightforward once you have practiced the technique. The device displays the measurement instantly on a small screen. The investment pays off if you are measuring a multi-room apartment or working alone.
Smartphone app (LiDAR)
iPhones from the 12 Pro model onwards, and some Android devices (such as the Samsung Galaxy S series with ToF sensors), include LiDAR scanners. Apps such as RoomScan Pro, Magicplan, or Canvas can generate a full measured floor plan in 5–10 minutes by walking around the room. Accuracy is typically within 1–5 cm — good enough for furniture planning and rough area calculations, but not sufficient for formal legal measurements such as a notarial surface Carrez certificate.
Smartphone app (camera-based)
Non-LiDAR apps use photogrammetry to estimate distances from images. They are less accurate than LiDAR — typically within 5–10 cm — but adequate for quick estimates. Several free options are available on both iOS and Android. Use these for rough furniture placement only, not for lease verification.
| Tool | Cost | Accuracy | Speed | Best for |
|---|---|---|---|---|
| Steel tape | 5–10 EUR | ±2–5 mm | Slow | Legal measurements |
| Laser meter | 20–60 EUR | ±1–2 mm | Fast | Large rooms / single person |
| Smartphone LiDAR | 0 EUR (device needed) | ±1–5 cm | Very fast | Furniture planning, floor plans |
| Camera app | Free | ±5–10 cm | Fast | Quick estimates only |
Step-by-step: measuring a room
Follow these steps for any room, whether rectangular or irregular. Have a pencil, paper, and your chosen measuring tool ready before you start.
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Step 1: Clear the perimeter
Move chairs, boxes, and rugs away from the walls. You need clear wall-to-wall access across the entire room. Furniture in the middle of the room does not affect the measurement, but objects against the walls will cause you to measure the wrong distance.
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Step 2: Sketch the room outline on paper
Draw a rough outline of the room before you take any measurements. Note any recesses, bay windows, built-in cupboards that project from the wall, or diagonal sections. You will measure these areas separately. The sketch does not need to be to scale — it is just a reference for recording numbers.
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Step 3: Measure each wall and record
For a rectangular room, measure two lengths and two widths. Place the tape or laser at the wall surface (not the skirting board). Record each measurement on your sketch immediately. Do not rely on memory.
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Step 4: Handle irregular rooms
Divide the floor plan into rectangles. Measure each rectangle separately. For diagonal sections (such as a room with a cut corner), measure the right-angle triangle formed: base times height, divided by 2. Add that figure to your rectangular areas.
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Step 5: Check ceiling height in sloped sections
If any part of the room has a sloped or angled ceiling — common in attic conversions — measure the ceiling height at the point where the slope meets the floor. Draw a line on your sketch marking where the ceiling height drops below 1.80 m. The floor area beyond that line does not count under French law.
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Step 6: Calculate the area
For each rectangle, multiply length by width to get the area in m². Sum all the rectangles for the total room area. Subtract any zones where the ceiling height is below 1.80 m. Repeat for every room in the apartment.
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Step 7: Record your total and compare
Add the adjusted room areas together. Record your total surface in m². Compare that figure against the surface habitable stated in your lease or the surface Carrez stated in your sale contract. A difference of more than 5% warrants follow-up.
Tip: Measure twice. A common transcription error is recording 3.45 m when you meant 3.54 m. Double-check each wall measurement before moving on to the next room. The few seconds this takes can save you a significant recalculation later.
French law: surface habitable vs surface Carrez
France uses two distinct legal definitions for floor area, each applicable in a different context. Understanding which one applies to your situation is important before you start measuring.
| Surface type | Used in | What counts | What is excluded |
|---|---|---|---|
| Surface habitable | Rental contracts (Loi Boutin 2009) | All floor space with ceiling height of at least 1.80 m, within the apartment walls | Structural walls, stairs, window recesses, balconies, terraces, garages, cellars, areas with ceiling height below 1.80 m |
| Surface Carrez | Property sales (co-ownership) | All private floor space of at least 8 m² with ceiling height of at least 1.80 m | Same exclusions as surface habitable, plus rooms individually under 8 m² |
Warning: If a rental contract states a surface habitable and the true area is more than 5% smaller, the tenant can demand a rent reduction proportionate to the discrepancy. This right is established under Article 3-1 of the Loi du 6 juillet 1989. The landlord has 2 months to contest the claim, after which the reduced rent applies retroactively from the date the tenant raised it.
The surface Carrez must be certified by a qualified géomètre-expert or diagnostiqueur for property sales. For rental contracts, the landlord is responsible for the stated surface habitable figure, but there is no legal requirement to have it professionally certified before signing the lease.
Measuring for furniture
Once you have the room dimensions, furniture planning is straightforward. A few additional measurements save significant frustration when delivery day arrives.
Record doorway widths and note whether doors open inward or outward. A sofa that fits the living room may not fit through a 75 cm doorway. Measure the width and depth of any corridor the furniture must pass through.
Note the position of power sockets, radiators, and gas points before deciding where to place large items. Moving a radiator is possible but expensive. Moving a sofa is free.
Measure window sill heights if you are buying curtains or blinds. Ceiling-to-floor curtains require a different track length than sill-length curtains.
Info: Free online floor plan tools such as Floorplanner and IKEA's room planner let you enter your room dimensions and drag and drop furniture to scale. Both tools are browser-based and require no download. They are useful for visualising a layout before committing to a purchase.
Frequently asked questions
Sources
- Legifrance — Loi n° 89-462 du 6 juillet 1989, Article 3-1 (surface habitable in rental contracts): legifrance.gouv.fr
- Legifrance — Loi n° 96-1107 du 18 décembre 1996 améliorant la protection des acquéreurs de lots de copropriété (Loi Carrez): legifrance.gouv.fr
- Service-public.fr — Surface habitable d'un logement: service-public.fr