Historical Evolution of Phone Number Digits
When Japan's telephone service launched in 1890 (Meiji 23), phone numbers were just 1 to 3 digits long. They expanded to 4 digits through the late Meiji and Taisho eras, grew to 5 digits between the late Taisho and early Showa years (Tokyo's telephone contracts passed 100,000 in 1930), and settled into the 10-digit landline and 11-digit mobile system after Tokyo's local exchange codes went to 4 digits in 1991 and Osaka's in 1999. The quick-reference table below shows which digit length belongs to which era. Understanding this evolution reveals the history of Japan's telecommunications infrastructure.
Digit changes had a major impact on users - requiring reprinting of business cards and advertisements, and updating registrations across services. The MIC (formerly the Ministry of Posts) ran large-scale public awareness campaigns with each change.
Quick Reference - Digit Lengths by Era (When were numbers 2, 4, or 6 digits?)
This table answers questions like "When were phone numbers 2 digits long?" and "When did 4- and 6-digit numbers appear?", broken down by digit count. The eras are based on Tokyo subscriber numbers, and timing varied by region.
| Subscriber number digits | Approximate era (Tokyo) | Background |
|---|---|---|
| 1 digit | Just after the 1890 launch | Numbers were assigned from "1" in order of application. The anecdote of who held Japan's first phone number "1" dates from this era |
| 2 digits | Launch to mid-Meiji | Cities with a few dozen subscribers managed with 2 digits; Yokohama had 42 subscribers at launch |
| 3 digits | Mid to late Meiji | Tokyo already had 155 subscribers at launch, using 3-digit numbers |
| 4 digits | Late Meiji to Taisho eras | Expanded to 4 digits in stages as subscribers surged |
| 5 digits | Late Taisho to early Showa years | Tokyo's telephone contracts passed 100,000 in 1930 (Showa 5), roughly 700,000 nationwide |
| 6 digits | Early Showa onward | 5 digits can express at most 99,999. Tokyo's contracts passing 100,000 in 1930 means subscriber numbers entered the 6-digit range |
| Current system with area codes (10-digit landlines) | Established through 1960s nationwide automatic dialing; Tokyo reached 10 digits in 1991, Osaka in 1999 | Area code + local exchange + subscriber number |
Major Digit Changes in History
Meiji to Early Showa - The Dawn of Telephony
When telephone service began in 1890 (Meiji 23) in Tokyo and Yokohama, subscriber numbers were just 1 to 3 digits. Tokyo had only 155 subscribers and Yokohama 42. Who held phone number "1"? is an anecdote from this era. Manual switchboard operators connected calls, and the numbering system was extremely simple.
As subscribers surged in the Taisho era, numbers gained digits step by step, and 5-digit numbers came into use between the late Taisho and early Showa years. Tokyo's telephone contracts passed 100,000 in 1930 (Showa 5), with roughly 700,000 nationwide, a scale that made 5-digit numbers indispensable. Automatic exchanges also began to be introduced in this period; Japan's first automatic switching system entered service at the Kyobashi branch of the Tokyo Central Telephone Office in 1926, allowing users to dial directly.
1950s to 1970s - Three-Digit Exchange Codes and Nationwide Automatic Dialing
The 1960s saw the establishment of the area code + local exchange + subscriber number system, enabling direct dialing nationwide. Local exchange codes also gained digits around this time: Tokyo's first 3-digit exchange code, "328", entered service at the Matsuzawa branch office in July 1956, and all of Tokyo's exchange codes switched to 3 digits in February 1960. Nationwide automation was completed in 1979, with Okinawa being the last region.
1990s - Area Code Consolidation
In the 1990s, area codes were changed in various regions to accommodate growing subscribers. Osaka unified its area code to 06 in 1999, changing local exchange numbers from 3 to 4 digits. Similar changes occurred in Nagoya (052), Sapporo (011), and Fukuoka (092).
1991 and 1999 - The 10-Digit Landline and 11-Digit Mobile Transitions
In Tokyo's 03 area, the first 4-digit local exchange codes appeared in the 23 wards in February 1988, and on January 1, 1991, all exchange codes switched from 3 to 4 digits, bringing landline numbers to 10 digits. On January 1, 1999, the Osaka-Hyogo 06 area followed with 4-digit exchange codes, and on the same day mobile numbers changed from 10 to 11 digits with the introduction of the 090 band. Together these changes affected approximately 60 million landline and 40 million mobile numbers.
2002-2013 - Mobile Band Expansion
The 080 band was added in 2002 as 090 numbers were expected to run out. In 2013, the 070 band (previously PHS-only) was opened to mobile phones.
Landline Number Structure
Japanese landlines consist of area code + local exchange + subscriber number, always totaling 10 digits. Area code lengths vary by region:
- 2-digit area codes: Tokyo (03), Osaka (06). Local exchange 4 digits + subscriber 4 digits
- 3-digit area codes: Yokohama (045), Nagoya (052), Sapporo (011). Local exchange 3 digits + subscriber 4 digits
- 4-digit area codes: Regional cities. Local exchange 2 digits + subscriber 4 digits
- 5-digit area codes: Small regions. Local exchange 1 digit + subscriber 4 digits
Number Exhaustion
With rapid mobile growth and IoT expansion, number exhaustion is a concern. Over 70% of the 270 million numbers across 090/080/070 are already allocated.
Countermeasures
- Opening the 060 band: Decided in December 2024; adds approximately 90 million numbers (not yet in service as of August 2026)
- Number recycling: Canceled numbers are reallocated after a dormancy period
- M2M-dedicated numbers: The 020 band (14 digits, ~80 billion numbers) is reserved for IoT devices
- eSIM utilization: Efficiently managing multiple numbers on one device
- IP phone (050) promotion: Encouraging 050 numbers for use cases that do not require mobile numbers
International Comparison
- United States: 10 digits (3-digit area code + 7 digits) under the North American Numbering Plan
- United Kingdom: 10-11 digits with flexible regional lengths
- China: Mobile 11 digits, landline 7-8 digits by region
- South Korea: Mobile 10-11 digits. Seoul's area code is 02, similar to Tokyo's 03
- Germany: Landline 3-12 digits with widely varying area code lengths
Japan's system is internationally well-organized, with area code length indicating regional scale. For international calls, add country code +81 and drop the leading 0, following the E.164 standard.
Future Outlook
With 5G and the explosive growth of IoT devices, number demand will continue to rise. The MIC is exploring fundamental revisions to the numbering system. Communication methods that do not rely on phone numbers - such as IP-address-based or user-ID-based calling (LINE, FaceTime) - are already widely used, and the traditional role of phone numbers is gradually evolving. However, as the means for emergency calls (110, 119) and contact with public institutions, phone numbers will remain a foundation of social infrastructure. Looking back at the history of digit lengths helps us understand the relationship between technological evolution and social change.