A room number is a number assigned to a room within a

building A building or edifice is an enclosed Structure#Load-bearing, structure with a roof, walls and window, windows, usually standing permanently in one place, such as a house or factory. Buildings come in a variety of sizes, shapes, and functions, a ...

. Its purpose is to identify a particular

room In a building or a ship, a room is any enclosed space within a number of walls to which entry is possible only via a door or other dividing structure. The entrance connects it to either a passageway, another room, or the outdoors. The space is ...

, and help building inhabitants locate that room. Room numbers may consist of three digits, but can be any number of digits. The room number is generally assigned with the first digit indicating the

floor A floor is the bottom surface of a room or vehicle. Floors vary from wikt:hovel, simple dirt in a cave to many layered surfaces made with modern technology. Floors may be stone, wood, bamboo, metal or any other material that can support the ex ...

on which the room is located.

Numbering systems

Similarly to how

house numbering House numbering is the system of giving a unique number to each building in a street or area, with the intention of making it easier to locate a particular building. The house number is often part of a Address (geography), postal address. The ter ...

systems vary depending on the region, room numbering systems do too. Some numbering systems inform the floor in which the room is located, but not all.

Floor + one digit

Some places in

Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

use a system in which the floor number is followed by only one number. In this system, apartment 52 is the second apartment on the 5th floor.

Floor + two digits

In many places, the number of a room is determined by the number of the floor followed by two digits that inform the number of the room itself, even if there are fewer than 10 rooms per floor. This system is used in the

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

by the

University of Hawaiʻi at Mānoa The University of Hawaii at Mānoa is a Public university, public Land-grant university, land-grant research university in Honolulu, Hawaii, United States. It is the flagship campus of the University of Hawaiʻi system and houses the main offic ...

for buildings with fewer than 99 rooms per floor. This way, the 5th's floor 2nd apartment would be number 502. In

Sweden Sweden, formally the Kingdom of Sweden, is a Nordic countries, Nordic country located on the Scandinavian Peninsula in Northern Europe. It borders Norway to the west and north, and Finland to the east. At , Sweden is the largest Nordic count ...

, floor numbers must have two digits, followed by two digits for the room number. Floor numbers start from 10 at ground level, and go down for underground floors, and up for above ground floors. In Sweden, the 5th's floor 2nd apartment would be number 1502.

Italy

Rome Rome (Italian language, Italian and , ) is the capital city and most populated (municipality) of Italy. It is also the administrative centre of the Lazio Regions of Italy, region and of the Metropolitan City of Rome. A special named with 2, ...

Italy Italy, officially the Italian Republic, is a country in Southern Europe, Southern and Western Europe, Western Europe. It consists of Italian Peninsula, a peninsula that extends into the Mediterranean Sea, with the Alps on its northern land b ...

, some addresses explicitly mention which floor ("''piano''") the apartment is located at. So an address could read "piano 5, interno 2" for the second apartment in the 5th floor.

References

building hotel terminology identifiers

number A number is a mathematical object used to count, measure, and label. The most basic examples are the natural numbers 1, 2, 3, 4, and so forth. Numbers can be represented in language with number words. More universally, individual numbers can ...

Hotel rooms {{architecture-stub