New Hampshire has 1 active area code serving the entire state across the Eastern Time Zone. The 603 area code, one of the original codes established in 1947, covers all communities from Manchester to the North Country. Whether you need to identify an unknown caller, plan business communications, or understand dialing requirements, this guide provides comprehensive and current information about the state’s unique single-area code system.
Key Takeaways:
- New Hampshire uses only one area code (603), making it one of just 11 US states with a single code
- The entire state operates in the Eastern Time Zone (EST/EDT)
- 10-digit dialing is mandatory for all calls within New Hampshire since October 2021
- Area code 603 is projected to remain viable until mid-2029 due to conservation efforts
- The state has strong cultural and economic ties to the 603 designation, treating it as a brand identity
New Hampshire Area Codes Quick Reference Table
| Area Code | Primary Coverage | Time Zone | Type | Year Introduced |
|---|---|---|---|---|
| 603 | The entire state of New Hampshire | Eastern (EST/EDT) | Original | 1947 |
Area Code 603: Complete Coverage
Area code 603 is New Hampshire’s only telephone area code and has been since the North American Numbering Plan was established. This single code serves approximately 1.38 million residents across all 10 counties and 234 municipalities.
Geographic Coverage
Area code 603 covers the entire state of New Hampshire without exception. This includes all 10 counties: Hillsborough, Rockingham, Merrimack, Strafford, Cheshire, Grafton, Belknap, Carroll, Sullivan, and Coös. The coverage extends from the Massachusetts border in the south to the Canadian border in the north, and from Vermont in the west to Maine and the Atlantic coast in the east.
Unlike most states, New Hampshire has never required a geographic split or overlay. The state spans approximately 9,350 square miles, making it the 46th largest state by area. Despite its relatively small size, the diverse geography includes urban centers, suburban communities, rural towns, and wilderness areas, all unified under the single 603 designation.
Historical Significance
Area code 603 was established on January 1, 1947, as one of the original 86 area codes created when AT&T and the Bell System implemented the North American Numbering Plan. At the time, the middle digit “0” indicated that the code served an entire state, while a middle digit “1” meant the code covered only part of a state.
The 603 area code has remained unchanged for over 77 years, an increasingly rare distinction in modern telecommunications. While many states have added multiple area codes due to population growth and the explosion of mobile devices, New Hampshire has maintained its single code through careful number management and conservation strategies.
The cultural significance of 603 extends beyond telecommunications. Businesses throughout the state have built their brands around the area code, from 603 Brewery in Londonderry to countless “Best of the 603” awards and competitions. The designation has become synonymous with New Hampshire identity, much like Vermont’s 802 or Maine’s 207.
Current Status and Conservation Efforts
The state faces ongoing challenges in preserving its single area code. The state has confronted potential exhaustion three times: in 2000, 2013, and most recently in 2023. Each time, conservation measures have successfully extended the code’s lifespan.
In October 2023, Governor Chris Sununu signed the “Don’t Overload the Code” executive order, directing the New Hampshire Department of Energy to investigate strategies for extending 603’s viability. The state estimates that adding a second area code could cost businesses nearly $500 million annually in rebranding, system updates, and lost brand equity.
Federal regulators initially projected exhaustion by 2027, but updated forecasts in October 2024 extended this timeline to mid-2029. The state legislature passed SB 603-FN in 2024, implementing additional conservation measures inspired by Maine’s successful efforts to preserve its 207 area code.
Conservation strategies include reducing robocaller number allocations, reclaiming unused number blocks from telecommunications carriers, improving forecasting accuracy, and implementing more efficient number pooling. The North American Numbering Plan Administration (NANPA) oversees these efforts at the federal level, while the New Hampshire Public Utilities Commission (NHPUC) manages state-level implementation.
Major Cities and Population
The 603 area code serves all New Hampshire cities and towns, including the state’s largest metropolitan areas. Manchester, the largest city with approximately 115,000 residents, serves as the state’s economic and cultural center. Nashua, the second-largest city with around 91,000 residents, has strong economic ties to the Greater Boston area.
Concord, the state capital with about 44,000 residents, houses state government operations. Portsmouth, a historic seacoast city of approximately 22,000, attracts tourists and maintains a vibrant downtown. Other significant communities include Dover, Rochester, Keene, Derry, Laconia, Lebanon, Claremont, and Berlin.
The statewide population of approximately 1.38 million makes New Hampshire the 41st most populous state. Despite modest population growth, the proliferation of mobile devices, business lines, and IoT devices has increased demand for telephone numbers exponentially.
Understanding Time Zones in New Hampshire
Time Zone Coverage
New Hampshire operates entirely within the Eastern Time Zone (ET). Every community in the state, from southern border towns to the northern reaches of Coös County, follows the same time zone. This uniformity simplifies scheduling and eliminates confusion for residents, businesses, and visitors.
The Eastern Time Zone is shared with neighboring Vermont and Maine, as well as the eastern portions of Massachusetts. This regional consistency facilitates business operations and personal communications across northern New England.
UTC Offset and DST
During Eastern Standard Time (EST), New Hampshire is UTC-5:00, meaning it is five hours behind Coordinated Universal Time. When Daylight Saving Time (EDT) is in effect from the second Sunday in March through the first Sunday in November, the state operates at UTC-4:00.
New Hampshire fully observes Daylight Saving Time without exceptions, unlike some states such as Arizona or Hawaii. All clocks move forward one hour in spring and back one hour in fall, affecting everyone uniformly throughout the state.
New Hampshire Cities and Their Area Codes
All New Hampshire cities use the 603 area code exclusively. The major communities include:
- Manchester (603) – Largest city, population ~115,000
- Nashua (603) – Second largest, population ~91,000
- Concord (603) – State capital, population ~44,000
- Derry (603) – Southern NH community, population ~34,000
- Dover (603) – Seacoast region, population ~32,000
- Rochester (603) – Strafford County seat, population ~32,000
- Keene (603) – Southwestern NH, population ~23,000
- Portsmouth (603) – Historic seacoast city, population ~22,000
- Laconia (603) – Lakes Region center, population ~16,000
- Lebanon (603) – Upper Valley region, population ~14,000
- Claremont (603) – Western NH, population ~12,500
- Berlin (603) – Northern NH, population ~9,400
This list represents the state’s most populous communities, but every town and city in New Hampshire, regardless of size, uses the same 603 area code.
How to Use Area Codes in New Hampshire
Since October 24, 2021, all calls within New Hampshire require 10-digit dialing (603-XXX-XXXX). This change was implemented nationwide to accommodate the 988 National Suicide Prevention Lifeline. Previously, many local calls could be completed using only the seven-digit local number.
You must dial the full 10 digits for all calls, whether calling across the street or across the state. This applies to both mobile and landline phones. Calls made with only seven digits will not connect and may result in a recorded message asking you to hang up and redial.
Emergency calls to 911 do not require an area code and should always be dialed with just three digits. The 988 mental health crisis line also requires only three digits and is available 24/7 for anyone experiencing a mental health emergency.
Calling Guidelines
Within state: Dial 603 + seven-digit local number for all calls within the state, even if calling your next-door neighbor.
From outside the state: Dial 1 + 603 + seven-digit local number. The “1” prefix indicates a long-distance call in the North American Numbering Plan.
International calls to New Hampshire: Dial your country’s international access code (often 00 or 011) + 1 (US country code) + 603 + seven-digit local number.
Mobile considerations: Mobile phone numbers in New Hampshire also use 603, but with number portability, a 603 number does not guarantee the person is currently in New Hampshire. People who move away often keep their 603 numbers, and newcomers may retain area codes from their previous locations.
Additional Resources
For the most current information about New Hampshire area codes and telecommunications regulations, visit the North American Numbering Plan Administration (NANPA) and the New Hampshire Public Utilities Commission. These official sources provide updates on number availability, conservation efforts, and any potential changes to the 603 area code.