Addresses around the world
Apartment, Unit and Floor Notation in Addresses
How to write flats, apartments, suites, floors and entrances in an address, and why placement and wording vary between regions.
Updated 14 October 2026 · 2 min read
Large buildings contain many separate homes and offices, so an address needs sub-building detail: flat, apartment, unit, suite, floor, entrance or room. The way this detail is written depends on the region.
Common terms
- Apartment / flat: a residential unit in a multi-unit building.
- Unit / suite: used for residential or commercial spaces.
- Floor / level: the vertical position within the building.
- Entrance / staircase / block: used where a complex has several access points.
- Room: common in hotels, dormitories and offices.
Where to place it
There are three common patterns:
- Same line, before the street number: e.g. unit number, then number and street.
- Same line, after the street: with a marker word.
- Separate line: above or below the street line.
All are valid in different places. Using the wrong placement can lead software to confuse the unit with the building number.
Floor counting
Some systems count the ground floor as zero, with the first floor above it. Others count the ground floor as the first floor. Where the difference matters, say clearly which floor you mean, and give the apartment number as well.
Entrances and blocks
Large residential complexes may be divided into blocks, buildings or staircases. Each has its own identifier. Always include the block or entrance if it exists; the apartment number alone may repeat across blocks.
Writing tips
- Use a clear marker word the destination recognises.
- Do not use symbols that may be misread.
- Keep the unit with the correct building number.
- For delivery, add a note such as an intercom code if the courier needs one.
Forms and data
In forms, a separate field for the unit helps both users and data quality. See address line 1 and address line 2 and address fields in online forms.
Summary
Sub-building detail is the last mile of an address. Write it where the destination expects it, count floors clearly and include blocks and entrances when they exist.
Frequently asked questions
Where should the apartment number go?
Follow the destination's convention. In some regions it follows the street line, in others it comes first, and it may be on its own line.
Are floor numbers counted the same everywhere?
No. In some places the ground floor is zero or marked separately, and the first floor is the one above it. In others, the ground floor is the first floor.