An Overview of Global Phone Number Systems
Phone numbers worldwide operate under the ITU's E.164 standard, with each country having its own country code and numbering plan. As globalization advances, understanding overseas systems benefits both business and travel. Overseas business primers are useful for context.
This article uses Japan's system as a baseline to compare major countries' characteristics. See also Japan's country code and how phone numbers work.
Basic International Dialing Rules
International numbers come in two formats.
- E.164 format:
+[country code][national number](e.g., +81-90-1234-5678 = Japan's 090-1234-5678) - International prefix format:
[int'l prefix][country code][national number](e.g., 010-81-90-1234-5678 from Japan)
The "+" denotes the originating country's international prefix. Smartphones interpret "+" as international regardless of country, so using "+" works whether you're calling Japan from abroad or vice versa.
Major Country Systems
Japan (+81)
10-digit landlines, 11-digit mobiles. Landlines are area code (1-4 digits) + exchange (1-4) + subscriber (4) = 10 digits. Mobiles start with 090, 080, 070, or 060 (11 digits) with no regional identification. Special numbers like 0120 and 0570 have separate systems.
United States (+1)
The US and Canada share the North American Numbering Plan (NANP) with country code +1. Numbers are fixed 10 digits: 3-digit area code + 3-digit exchange + 4-digit subscriber. No landline/mobile distinction in the number itself. Area codes include 212 (NYC), 213 (LA), 415 (SF). Toll-free numbers use 800, 888, 877, 866, etc.
United Kingdom (+44)
"Leading 0 + area code + subscriber number," totaling 10-11 digits. London uses 020, Manchester 0161, Edinburgh 0131. Mobiles start with 07 (11 digits). Freephone uses 0800/0808; premium-rate uses 0870/0871/09 - granular categorization.
China (+86)
Landlines use "city code + subscriber" for 10-12 digits. Beijing is 010, Shanghai 021, Guangzhou 020. Mobiles start with 13/14/15/17/18/19 (11 digits), subdivided by carrier (China Mobile, Unicom, Telecom). Domestic international prefix is 00.
South Korea (+82)
"Leading 0 + area code + subscriber," 9-11 digits. Seoul uses 02, Busan 051, Daegu 053. Mobiles are unified to "010" (11 digits) - older 011, 016, etc. were consolidated into 010. The structure mirrors Japan and is straightforward.
India (+91)
Landlines use "STD code (2-4 digits) + subscriber" totaling 10 digits. Delhi is 11, Mumbai 22, Bangalore 80. Mobiles start with 6, 7, 8, or 9 (10 digits). With the world's second-largest mobile market, India has expanded its numbering plan repeatedly to address rapid number exhaustion.
Key Differences from Japan
Digit counts
Japan: 10-digit landlines, 11-digit mobiles. US/Canada: fixed 10. China mobile: 11; landlines 10-12. India: 10 across the board.
Regional identification
Japan uses "area codes" for regional identification - the same as US "area codes" or China's "city codes." Some countries (Japan, Korea, India) have no regional identification in mobile numbers; others (US, Canada) apply area codes to mobiles too.
Distinguishing fixed vs mobile
Japan: leading digits (090/080/070/060 = mobile). US: indistinguishable by number alone. UK: anything starting with 07 is mobile. See Japanese mobile number basics for more.
Emergency numbers
Japan: 110 (police), 119 (ambulance/fire). US: 911. UK: 999. EU common: 112. See emergency numbers around the world. Always look these up before traveling.
Things to Watch When Calling Internationally
Cost differences
International rates vary widely by origin, destination, and carrier. Japan-to-overseas landline calls run dozens to hundreds of yen per minute, with mobile origination higher still. IP calling apps (LINE, Skype, WhatsApp) are effectively free over Wi-Fi.
Mind the time difference
Tokyo is 14 hours ahead of US Eastern, 9 hours ahead of UK, 3.5 hours ahead of India. Confirm the destination's local time falls within business hours before calling.
Beware international scam calls
Suspicious calls from foreign country codes like +1 or +44 may be international call scams. Don't return calls from unfamiliar numbers, especially those outside +81 (Japan).
Living or Working Abroad
If you want to keep your Japanese number while overseas, the standard approach is using a SIM-free phone with a local SIM while receiving Japanese-number calls via VoIP. Services like Rakuten Mobile, IIJmio, and My050 let you keep your Japanese number working abroad. Virtual phone numbers are also useful for international communication. For long-term stays, obtaining a local number simplifies signups for local services and emergency contact.