Area code 313 was assigned in 1947 as one of the original area codes. It first covered the southeast part of Michigan. Two splits, in 1993 and 1997, shrank it to Detroit and a group of nearby suburbs, and in 2025 the 679 overlay joined it on the same territory.
Quick answer
- 313 was assigned in 1947 for southeast Michigan. Today it covers Detroit and a list of closest suburbs named by the Michigan Public Service Commission (MPSC).
- It was split twice: 810 in 1993 and 734 in 1997. It has not been split since.
- The MPSC approved a 679 overlay on May 18, 2023. Existing 313 numbers do not change.
- All local calls require 10 digits since October 7, 2025. 679 numbers may be assigned starting November 7, 2025, but the MPSC says they go to new customers only after 313 numbers are exhausted.
The essentials
313 area code: quick facts
| Area code | 313 |
| Coverage | Detroit, Hamtramck, Highland Park, and nearby suburbs named by the MPSC |
| State | Michigan |
| Time zone | Eastern Time (ET) |
| Assigned | 1947, one of the original area codes |
| Splits from 313 | 810 (1993) and 734 (1997) |
| Overlay code on the same territory | 679, approved May 18, 2023; may be assigned from November 7, 2025 |
| Dialing | 10 digits for local calls since October 7, 2025 |
| Country code | +1, the country code for the North American Numbering Plan |
How 313 became Detroit's code
- 1947: Area code 313 is assigned to Michigan as one of the original area codes of the North American Numbering Plan. The MPSC says it covered the southeast portion of the state.
- 1993: The first split creates area code 810. The FCC lists 810 as opening in December 1993.
- 1997: The second split creates area code 734. The FCC lists 734 as opening in December 1997.
- 1999: The numbering administrator (NANPA) tells the MPSC that 313 is running out of numbers and that relief must be planned. The MPSC names dial-up internet, fax lines, and cellular growth as reasons.
- 2000: NANPA, for the industry, petitions for relief and recommends an all-services overlay. NANPA reserves 679 for it (MPSC case U-12880).
- September 7, 2001: The MPSC issues an order approving the overlay concept. Number conservation and other relief projects then let the plan wait more than 20 years.
- November 16, 2022: NANPA files a new petition (MPSC case U-21337), because 313 is again approaching exhaustion.
- May 18, 2023: The MPSC approves the 679 overlay.
- April 7, 2025: A six-month period of permissive 10-digit dialing begins.
- October 7, 2025: Ten-digit dialing becomes mandatory for local calls.
- November 7, 2025: 679 numbers may be assigned to new service in the 313 area.
Where area code 313 is used
The MPSC says 313 covers Detroit and its enclaves of Hamtramck and Highland Park, plus the suburbs of Allen Park, Dearborn, Dearborn Heights, Ecorse, the Grosse Pointes, Inkster, Lincoln Park, Redford Township, River Rouge, and Taylor. Those are the communities the regulator names in its 2023 hearing materials and again in its 2025 release.
The MPSC sources do not give a county list or street boundaries. Wikipedia's article on the 313 and 679 codes also lists Harper Woods and Melvindale, and says only part of Taylor is included (north of Goddard Road and east of Holland Road). Those details are not in the MPSC materials we checked, so confirm a specific address with your phone provider before you assume its area code.
Why 313 needed relief, and why an overlay was chosen
An area code has 792 available prefixes, each holding 10,000 numbers, according to the MPSC staff FAQ. As providers receive prefixes, the code nears exhaust and a new code is needed for that geography.
313 has been close to exhaust before. NANPA warned the MPSC in 1999 that numbers were running low. The MPSC presentation lists dial-up internet, fax lines, and growth in cellular service as the causes. The two 1990s splits changed numbers for customers who moved to the new codes. The MPSC says an overlay avoids that, because existing customers keep their area code and number.
Number conservation and relief projects in the early 2000s delayed the need for the overlay. NANPA's November 2022 petition projected exhaust in the third quarter of 2025. The projection has moved since, as the table shows. The MPSC's September 2025 release says the timing is "subject to change due to telephone numbering demand."
| MPSC statement | Projected exhaust of 313 |
|---|---|
| January 19, 2023 release | Third quarter of 2025 |
| May 18, 2023 approval | Second quarter of 2026 |
| March 17, 2025 release | Fourth quarter of 2027 |
| September 16, 2025 release | First quarter of 2028 |
NANPA projects that the overlay will provide relief for approximately 46 years, per the MPSC staff FAQ.
Neighboring area codes in Michigan
The MPSC says 313 was split twice. The table shows what the official sources say about the codes tied to 313. The MPSC materials do not describe where each neighbor code applies, so the territory notes come from Wikipedia and are labelled.
| Code | Relation to 313 | Territory |
|---|---|---|
| 313 | Original 1947 code for southeast Michigan | Detroit and the suburbs listed above |
| 679 | Overlay on 313, approved May 18, 2023 | Same territory as 313 |
| 810 | Created by the 1993 split (FCC: opened December 1993) | Per Wikipedia, the northern portion, including Flint and the southern Thumb |
| 734 | Created by the 1997 split (FCC: opened December 1997) | Per Wikipedia, the western portion, including Ann Arbor and Monroe County |
| 248 and 947 | Not a 313 split. The MPSC cites 947 as an existing Michigan overlay on 248 | Not described in the sources checked |
The 679 overlay and what it changes
An overlay puts a second area code on the same geography. The MPSC staff FAQ says current customers keep their area code and number, and that numbers from the new code may be assigned to new customers or to those adding lines.
- Existing numbers: they do not change. The MPSC says the 313 area code is not going away.
- Local calls stay local: the MPSC says the price of a call, the coverage area, and other rates and services do not change because of the overlay.
- Calls between 313 and 679: the MPSC presentation says both codes can make local calls to each other.
- When 679 is assigned: the MPSC says new lines or services may be assigned 679 starting November 7, 2025, but 679 numbers go to new customers only once 313 numbers are exhausted. Providers can keep assigning 313 numbers from existing inventory, and returned numbers are reassigned.
| Code | Added | Where it applies |
|---|---|---|
| 313 | 1947 | Detroit and nearby suburbs, original code |
| 679 | Approved May 18, 2023; may be assigned from November 7, 2025 | Overlay on the 313 area |
Time zone and daylight saving time
Area code 313 uses Eastern Time. The tz database zone table lists Detroit as America/Detroit, labeled "Eastern - MI (most areas)." The same table lists a separate Michigan zone, America/Menominee, as Central time on the Wisconsin border. That zone is not in the 313 area.
Daylight saving time starts at 2:00 a.m. on the second Sunday of March and ends at 2:00 a.m. on the first Sunday of November. The NIST page says these rules were enacted by the Energy Policy Act of 2005. In 2026, NIST gives March 8 and November 1 as the change dates.
How to dial a 313 number
North American numbers have three parts: a country code, a three-digit area code, and a seven-digit local number. NANPA says the ITU assigned country code 1 to the NANP area.
Since October 7, 2025, all local calls within the 313 area code must use 10 digits, including the area code. The MPSC says seven-digit calls will not be completed and callers may hear a recording asking them to hang up and redial with 10 digits. Long-distance calls continue to use 1 plus the area code and number. You can still dial three digits for 911 and 988, and for 211, 311, 511, and 811 where available.
The MPSC advises customers to reprogram equipment that dials only seven digits. Its examples include life-safety systems, medical alert devices, alarm and security systems, fax machines, gates, speed dialers, mobile phone contact lists, call forwarding settings, and voicemail services. Its business guidance adds PBXs and routing or toll-restriction systems.
Caller ID and scams with a 313 number
The FTC warns that "Scammers can make any name or number show up on your caller ID." The FTC calls this spoofing. Scammers can also match the first six digits of your own number, which the FTC calls neighbor spoofing.
- If you pick up and do not recognize the caller, the FTC advises that you hang up.
- Letting an unknown call go to voicemail is one option.
- The FTC says call blocking is your best defense against unwanted calls.
A 313 number shows the code that was assigned, not who is calling or where they are. The sources checked do not say that 313 numbers are targeted more than other codes. Because 679 will share the same territory, a 313 or 679 caller ID is not a reliable sign that the caller is in Detroit.
Business numbers in the 313 area
313 identifies the Detroit area. Wikipedia notes that opponents of the overlay cited the cultural importance of 313, which it says is often treated as synonymous with the city. That is a Wikipedia statement and is not confirmed by the MPSC.
The MPSC says providers may still have 313 numbers in inventory as 679 rolls out, and that returned 313 numbers are recycled. Which code a new line gets depends on the provider's inventory and the numbering pool, so ask before you plan a campaign or print a number on materials.
Because 313 and 679 share one territory and can call each other locally, route calls by team or extension, not by area code. The MPSC also says costs to update customer equipment for 10-digit dialing are the customer's responsibility.
Important: Whether a specific 313 number can be assigned to your business depends on your phone provider and its current inventory. This guide does not make claims about availability.
Before you use a 313 number
- Confirm the number is available from your provider, and get its terms in writing.
- Ask who owns the number and whether it can be moved to another provider if you switch.
- Ask whether a new line would be a 313 or a 679 number.
- Use 10-digit dialing on every system, including PBXs, fax machines, alarms, call forwarding, and voicemail. The MPSC says seven-digit calls are no longer completed.
- Print the full 10-digit number on stationery, cards, and advertising.
- Route calls by team or extension, because 313 and 679 share one territory.
- Check each site's address. The MPSC names communities, not street boundaries, so confirm the address with your provider.
- Plan for caller ID. A 313 number does not prove who is calling, and neighbor spoofing copies the first six digits of your own number.
Frequently asked questions
Which area is the 313 area code for?
Area code 313 serves Detroit, its enclaves Hamtramck and Highland Park, and the suburbs of Allen Park, Dearborn, Dearborn Heights, Ecorse, the Grosse Pointes, Inkster, Lincoln Park, Redford Township, River Rouge, and Taylor, according to the Michigan Public Service Commission (MPSC). It was assigned in 1947 and once covered the southeast part of the state.
Is area code 313 being split or replaced?
No. The MPSC approved a 679 overlay on May 18, 2023, and said the overlay was preferable to a geographic split. Current 313 customers keep their numbers and the 313 area code. Splits in 1993 and 1997 created 810 and 734, but those were earlier changes.
Do I need to dial 10 digits for a 313 number?
Yes. Since October 7, 2025, all local calls within the 313 area code must use 10 digits, including the area code. The MPSC says calls placed with only seven digits will not be completed. Long-distance calls still use 1 plus the area code and number. You can still dial three digits for 911 and 988.
Will a new line in Detroit get a 679 number?
Possibly, but not yet. The MPSC says 679 numbers may be assigned starting November 7, 2025, and that they will go to new customers only once 313 numbers are exhausted. Its September 2025 release projects that exhaust for the first quarter of 2028, subject to change. Ask your provider which code a new line would get.
Does a 313 number mean the caller is in Detroit?
Not always. The FTC says scammers can make any name or number show up on caller ID, and neighbor spoofing copies the first six digits of your own number. A local-looking number is not proof of who is calling.
Sources · reviewed October 2026
MPSC news release, March 17, 2025 and MPSC news release, September 16, 2025
Used for the April 7, 2025 start of permissive dialing, mandatory 10-digit dialing from October 7, 2025, the November 7, 2025 date for 679, the rule that 679 goes to new customers after 313 is exhausted, the exhaust projections of the fourth quarter of 2027 and the first quarter of 2028, the 911 and 988 note, and the equipment guidance. The michigan.gov pages block automated requests, so the text was read from archived copies.
MPSC news release, January 19, 2023, MPSC news release, May 18, 2023, and MPSC notice of public hearing, case U-21337
Used for the list of communities in 313, the May 18, 2023 approval of the 679 overlay, the third-quarter-2025 and second-quarter-2026 projections, the preference for an overlay over a split, the 1999 NANPA warning, the September 7, 2001 order, and the November 16, 2022 petition.
313 Area Code Overlay presentation, MPSC, March 9, 2023 and Area Code Overlay Information and FAQs, MPSC staff
Used for the 1947 assignment as one of the original codes, the 1993 and 1997 splits, case U-12880, the causes of the 1999 shortage, calls between 313 and 679 being local, the 792 prefixes of 10,000 numbers each, and the 46-year relief estimate. The PDFs block automated requests, so the text was read from archived copies.
Numbering Resource Utilization in the United States, FCC, Table 6 and About NANPA, archived copy
Used for the opening dates of 313 (January 1947), 810 (December 1993), and 734 (December 1997). The archived NANPA page supports the country code 1 for the NANP area.
Area codes 313 and 679, Wikipedia
Weak support only, not confirmed by the regulator. Used for the extra communities (Harper Woods, Melvindale, part of Taylor), the territories of 810 and 734, and the cultural-significance remark.
Phone Scams, FTC Consumer Advice and That's not your neighbor calling, FTC Consumer Alert
Used for the spoofing definition, the neighbor spoofing explanation, the advice to hang up on unknown callers, the voicemail option, and the call-blocking advice.
Daylight Saving Time, NIST and tz database zone table
Used for the second-Sunday-of-March and first-Sunday-of-November rule, the Energy Policy Act of 2005, the 2026 change dates, and the America/Detroit zone entry labeled "Eastern - MI (most areas)."