Area Code 143 – Muroran, Hokkaido

Overview of Area Code 143

Area code 143 is a geographic numbering plan area (NPA) within the Japanese telephone numbering plan, assigned to the city of Muroran and its surrounding municipalities in the Iburi Subprefecture of Hokkaido. This code is part of the ITU-T E.164 international numbering framework, where Japan's country calling code is +81. When dialing from abroad, callers must replace the leading zero with the country code, resulting in the international format +81 143 XX-XXXX.

Geographic Coverage and Administrative Jurisdiction

The 143 area code covers Muroran City, the administrative and industrial hub of the region, as well as neighboring towns such as Date, Sobetsu, Toyako, and portions of Abuta District. Muroran is known for its steel production and port facilities, while the surrounding areas include volcanic landscapes and Lake Toya, a popular tourist destination. The region falls under the jurisdiction of Hokkaido Prefecture, and the numbering plan is administered by the Ministry of Internal Affairs and Communications (MIC) in Japan.

Dialing Formats and Instructions

Within Japan, local calls within the 143 area code are made using the subscriber number only, which is typically 6 digits long. For example, calling a local number such as 123-4567 requires no area code. However, when calling from outside the area code but still within Japan, the full national number must be dialed: 0143-123-4567. The leading zero is part of the national trunk prefix and is not included when dialing from overseas. International callers should dial +81 143 123-4567, omitting the initial zero.

Overlay and Numbering Considerations

As of the latest data, area code 143 has not been overlaid with another area code, meaning that local calls within the region do not require the area code. However, the Japanese numbering system is undergoing gradual changes to accommodate increasing demand for numbers, and future overlays are possible. For now, the standard 10-digit national format (0XX-XXX-XXXX) applies, with the area code being 3 digits (143) followed by a 6-digit subscriber number.

Caller Instructions

For local callers within Muroran and the surrounding area, simply dial the 6-digit subscriber number. For callers from other parts of Japan, dial 0143 followed by the subscriber number. For international callers, dial the international access code (e.g., 011 from the US, 00 from most European countries), then Japan's country code 81, then 143, and finally the subscriber number. It is important to note that the leading zero of the area code is dropped in international dialing.