The +1671 area code is for Guam, a US unincorporated territory in the Western Pacific. Guam is the largest island in Micronesia, with about 170,000 residents, most living in the northern villages around Dededo and the capital Hagåtña. The island has a major US military presence (Andersen Air Force Base and Naval Base Guam together take up about a third of the island) and close ties to Japan, the Philippines, and the rest of the Mariana Islands chain. Guam uses the North American Numbering Plan with area code 671, but calls from the US mainland are typically billed as international.
Quick answer: Guam's area code is 671 within the NANP. Dial 1-(671)-XXX-XXXX from the US or Canada. Phone numbers are 10 digits (including the area code). There is no trunk prefix beyond the standard NANP "1." From outside North America, dial your exit code + 1-671 + 7-digit number.
How to call Guam: quick reference
Guam is part of the NANP, so the dialing format is the same as calling any US number: country code 1, area code 671, then the 7-digit local number.
| Calling from | Dialing format |
|---|---|
| US/Canada | 1-(671)-XXX-XXXX |
| Japan | 010-1-671-XXX-XXXX |
| Philippines | 00-1-671-XXX-XXXX |
| Australia | 0011-1-671-XXX-XXXX |
| UK | 00-1-671-XXX-XXXX |
| CallSky app | +1671XXXXXXX |
Understanding Guam phone numbers
Guam phone numbers follow the standard NANP format: area code 671 + 7-digit local number. All calls on the island use this single area code.
Landline numbers
Landline prefixes include 472, 475, 477, 632, 633, 634, 635, 646, 647, 648, 649, and others. GTA TeleGuam is the primary landline provider. Landline numbers are 7 digits after the 671 area code, just like any other NANP number.
Mobile numbers
Mobile prefixes include 483, 486, 487, 488, 689, 727, 777, 788, 797, 898, and others. The three main mobile carriers each have their own prefix ranges, but number portability means you can't always identify the carrier from the prefix.
Mobile carriers in Guam
GTA TeleGuam
The island's oldest telecom, handling both fixed-line and mobile service. GTA provides 4G LTE coverage across the island and is the main landline provider. It was acquired by Teleguam Holdings in 2016.
Docomo Pacific
A subsidiary of Japan's NTT Docomo, and one of Guam's two major mobile competitors. Docomo Pacific has strong ties to Japan and also operates in the CNMI. It offers 4G LTE and has been expanding its network.
IT&E
The other major mobile carrier, also operating across Guam and the CNMI. IT&E provides 4G LTE service and competes closely with Docomo Pacific and GTA for mobile subscribers.
Don't confuse +1671 with nearby codes
| Code | Territory | Why it's confused |
|---|---|---|
| +1670 | Northern Mariana Islands | Neighboring US territory, one digit apart (670 vs 671) |
| +1684 | American Samoa | Another US Pacific territory with a 1+6xx area code |
| +63 | Philippines | Large Filipino community on Guam; people mix up the codes |
The +1670 (CNMI) vs +1671 (Guam) confusion is the most common. Both are US territories in the Mariana Islands, just a short flight apart, but they have separate area codes. If you're trying to reach Saipan, that's 670, not 671.
Time zone considerations
Guam is in Chamorro Standard Time (ChST), UTC+10. There is no daylight saving time. Guam is one of the first US territories to see each new day, 15 hours ahead of Eastern Time (or 14 during US daylight saving).
| Your time zone | Time in Guam (ChST, UTC+10) | Best calling window |
|---|---|---|
| New York (EST, UTC-5) | +15 hours | Late afternoon your time (morning in Guam) |
| Los Angeles (PST, UTC-8) | +18 hours | Early afternoon your time |
| Tokyo (JST, UTC+9) | +1 hour | 9 AM - 9 PM your time |
| Manila (PHT, UTC+8) | +2 hours | 9 AM - 7 PM your time |
| Sydney (AEDT, UTC+11) | -1 hour | 9 AM - 9 PM your time |
| Honolulu (HST, UTC-10) | +20 hours | Early afternoon your time |
The gap from the US mainland is substantial. When it's 5 PM Friday in New York, it's 8 AM Saturday in Guam. If you're calling from the mainland US, your best bet is late afternoon or evening your time, which catches Guam in the morning.
Communication in Guam
Business hours and culture
Business hours are generally 8 AM to 5 PM, Monday through Friday, similar to the US mainland. Government offices follow US federal schedules. Guam observes US federal holidays plus some local ones like Guam Discovery Day (first Monday in March) and Liberation Day (July 21). English and Chamorro are the official languages, with Filipino also widely spoken.
Network quality
Guam has good mobile and internet infrastructure for its size. All three carriers provide 4G LTE coverage across the main population areas. The island is a major submarine cable hub in the Pacific, with multiple cables connecting to Japan, Australia, and the US mainland. International call quality is generally good.
Messaging habits
Standard US messaging apps dominate: iMessage, Facebook Messenger, and WhatsApp. Given the large Filipino community, Viber is also used. The military community tends to use whatever platforms are popular stateside.
The Guam diaspora
Where Chamorros and Guam residents live abroad
There are more Chamorros (the indigenous people of Guam) living on the US mainland than on the island itself. Major communities exist in California (especially San Diego, the Bay Area, and Sacramento), Washington state, Nevada, and Texas. Many Chamorros also serve in the US military at rates well above the national average, which disperses families across bases worldwide.
Why they call
Family is central to Chamorro culture. Fiestas (village celebrations), funerals, christenings, and rosaries bring families together, and those who can't attend in person call in. Liberation Day (July 21, marking the 1944 liberation from Japanese occupation) is a major occasion for calls home. Military families posted away from Guam also make regular calls back to the island. The time difference from the US mainland makes scheduling difficult, so weekend calls are common.
Dialing examples
Calling a Guam number from the US mainland
To reach a Guam number like 671-632-1234, dial: 1-671-632-1234. This is the same format as calling any US number, but your carrier will likely bill it as international.
Calling Guam from Japan
To call a Guam number like 671-483-5678, dial: 010-1-671-483-5678 from a Japanese landline, or +1-671-483-5678 from a mobile.
Calling Guam from the Philippines
To reach a Guam number like 671-727-9012, dial: 00-1-671-727-9012, or +1-671-727-9012 from a mobile.
Calling within Guam
For local calls within Guam, dial the 7-digit number directly: 632-1234. You don't need the area code or the "1" prefix for on-island calls.
Common mistakes to avoid
Assuming Guam calls are free domestic calls
Guam uses the NANP and you dial it like a US number (1-671-XXX-XXXX), but most US carriers treat calls to Guam as international. Check your plan before calling, or you may see unexpected charges on your bill.
Confusing 670 (CNMI) with 671 (Guam)
These area codes are one digit apart. 670 reaches Saipan, Tinian, and Rota in the Northern Mariana Islands. 671 reaches Guam. If you dial the wrong one, you'll reach the wrong territory.
Forgetting the 15-hour time gap from the East Coast
Guam is a full day-cycle ahead of the US mainland. When you call at 9 AM Monday in New York, it's midnight Monday-Tuesday in Guam. Plan your calls for US late afternoon to catch Guam in the morning.
Dialing 011 before 1-671 from the US
Since Guam is in the NANP, you dial 1-671-XXX-XXXX from the US, not 011-1-671-XXX-XXXX. The 011 international access code is for non-NANP countries. Adding it for Guam may cause the call to fail or route incorrectly.
Prefer calling over WiFi? See our guide to the best apps for WiFi calling.
Frequently asked questions (FAQ)
What country code is +1671?
+1671 is the area code for Guam, a US unincorporated territory in the Western Pacific. Guam uses the North American Numbering Plan (NANP) with area code 671.
Is calling Guam the same as calling within the US?
The dialing format is the same (1-671-XXX-XXXX), but most US carriers bill Guam calls as international, not domestic. Check your plan's international rates or use a service like CallSky.
What is the difference between +1670 and +1671?
+1670 is the Northern Mariana Islands (CNMI) and +1671 is Guam. They are neighboring US territories in the Mariana Islands chain but have separate area codes.
What time zone is Guam in?
Guam is in Chamorro Standard Time (ChST), UTC+10. There is no daylight saving time. Guam is 15 hours ahead of US Eastern Time.
How much does it cost to call Guam?
With CallSky, calls to Guam start at $0.06/min on the Economy plan and $0.08/min on the Premium plan.
Looking for other Pacific dialing guides? See Northern Mariana Islands (+1670), American Samoa (+1684), or browse all country codes.