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. When calling Japan from abroad, you prefix the country code +81.
Digit changes had a major impact on users. Because numbers appeared on business cards and advertisements and were registered with many services, each change required reprinting and updating on a large scale.
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 subscriber count reached that scale, and numbers came to be expressed by combining an exchange code with a subscriber number |
| 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, so short numbers were enough. 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: in Tokyo, exchange codes became 3 digits in February 1960.
Nationwide automation was completed in 1979, making operator-free direct calling possible across Japan. Area code lengths range from 2 to 5 digits depending on the region.
1990s - Area Code Consolidation
In the 1990s, area codes and local exchange codes were revised 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.
1991 and 1999 - The 10-Digit Landline and 11-Digit Mobile Transitions
In Tokyo's 03 area, all exchange codes switched from 3 to 4 digits on January 1, 1991, 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 , taking on the current 11-digit format beginning with 090.
The changes reached both landline and mobile numbers, so business cards, advertisements, and registered contact details had to be updated widely.
2002-2013 - Mobile Band Expansion
As mobile phones spread, the 080 band was added in 2002. In 2013, the 070 band, previously used for PHS, was opened to mobile phones as well.
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
Three area codes are 2 digits long: Tokyo's 23 wards (03), the area around Kashiwa in Chiba and Tokorozawa in Saitama (04), and Osaka City (06). Because the total is fixed at 10 digits, a shorter area code leaves more digits for the local exchange and subscriber number.
Number Exhaustion
With mobile growth and the increase in IoT devices, number exhaustion is a concern. The 090, 080, and 070 bands together provide about 270 million numbers, and as of 2026 roughly 265 million have been assigned to carriers. The 090 and 080 bands have used up their assignable numbers, and over 90% of the 070 band is assigned as well. Note that numbers assigned to carriers and actual subscriptions are different figures: mobile subscriptions total about 233 million (end of March 2026).
Countermeasures
- Opening the 060 band: In December 2024 the MIC revised the telephone numbering plan to add the 060 band for mobile phones, adding roughly 90 million numbers (not yet in service as of August 2026)
- Number recycling: Canceled numbers are reallocated after a dormancy period, using the number resource efficiently
- A band dedicated to data transmission (020): The 020 band is provided for data communication such as IoT devices, reducing consumption of mobile numbers. The format beginning with 0200 is 14 digits and covers about 10 billion numbers. This band is limited to uses that do not connect voice calls
- eSIM utilization: Managing multiple numbers efficiently on one device avoids wasting numbers
- IP phone (050) promotion: For uses that do not require a mobile number, 050 numbers are encouraged
International Comparison
Digit lengths differ from country to country, and comparing other numbering plans makes the characteristics of Japan's system clearer.
- United States: 10 digits excluding the country code (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
A distinctive feature of Japanese landlines is that the total always comes to 10 digits even though area code lengths differ by region. For international calls, add Japan's country code +81 and drop the leading 0 (see Guide to Japan's Country Code +81 for details). This conversion rule follows the worldwide E.164 recommendation.
The State of Number Resources as of 2026
Demand for numbers is growing along with the spread of IoT devices, and the December 2024 revision of the telephone numbering plan added 060 as a band for mobile phones. As of August 2026, 060 numbers are not yet in service.
Communication methods that do not rely on phone numbers are also widespread: IP-address-based communication and user-ID-based calling services (LINE, FaceTime) are used daily. At the same time, emergency calls (110, 119) and contact with public institutions rely on phone numbers, so the numbering system remains part of the social infrastructure as of 2026.