Area Code 237 – Thanh Hoa province

Overview of Area Code 237 (Thanh Hoa Province)

Area code 237 is the National Destination Code (NDC) assigned to the landline telephone network of Thanh Hoa Province, located in the North Central Coast region of Vietnam. This geographic code is used for fixed-line services within the province, covering the provincial capital Thanh Hoa City as well as all districts and rural areas under the provincial jurisdiction. The code is part of the Vietnamese national numbering plan, which follows the ITU-T E.164 international standard.

Geographic Coverage and Administrative Jurisdiction

Thanh Hoa is the largest province in Vietnam by area, and its telephone network serves a population of over 3.6 million people. The area code 237 applies to all fixed-line subscribers within the province, including the cities of Thanh Hoa, Sam Son, and Bim Son, as well as the districts such as Dong Son, Hoang Hoa, and Tho Xuan. The province borders Nghe An to the south, Son La and Hoa Binh to the north, and Ninh Binh to the north-east, with a coastline along the South China Sea.

Dialing Formats

For local calls within Thanh Hoa province, subscribers dial the subscriber number directly, which typically consists of 7 digits (e.g., 123 4567). For calls from other provinces within Vietnam, the trunk prefix 0 is used followed by the area code and subscriber number: 0237 123 4567. For international callers, the Vietnamese country code +84 is used, followed by the area code without the leading zero: +84 237 123 4567. It is important to note that the area code is not separated by a space or hyphen in international format; the entire number is dialed as a continuous sequence.

Overlay and Numbering Considerations

Currently, there is no overlay code for Thanh Hoa; the 237 code is the sole geographic code for the province. However, due to the growth of fixed-line services, the province has implemented a 10-digit dialing plan for all national calls, which includes the trunk prefix 0 and the area code. This is consistent with the national plan introduced in 2017, which standardized all Vietnamese fixed-line numbers to a uniform length.

Caller Instructions

For callers within Vietnam, always include the trunk prefix 0 when dialing from a different province or from a mobile phone. For example, to call a fixed line in Thanh Hoa from Hanoi, dial 0237 123 4567. For international callers, replace the leading 0 with the +84 country code: +84 237 123 4567. Ensure that you have the correct subscriber number, as fixed-line numbers in Thanh Hoa are 7 digits long.

For those using VoIP services or internet-based calling, the same international format applies. Always verify the number with the recipient, as misdialing the area code may route your call to a different province.