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zipcodes.pro — AREA-CODE/312

312 area code

Area code 312 is in Illinois. It covers Chicago, Wheeling, Westmont and 5 other places: 91 ZIP codes in Cook and DuPage counties. Local time there is , Central Time. In service since 1947; 872 (2009) overlays it, so a number from there can have either code.

Time zone
Central
Largest city
Chicago
Overlays
872
In service since
1947
Rate centres
8
Prefixes assigned
784 (7,840,000 numbers)

Who calls from a 312 number

NANPA records the carrier each block of 312 numbers is assigned to. Of the 7.6 million 312 numbers assigned, 39% are with local phone companies (AT&T); 28% with mobile carriers (T-Mobile, AT&T Mobility and Verizon Wireless); 27% with cable, internet-calling, business and other carriers (Level 3 and Verizon Business); 6% with paging companies.

That is who the numbers were assigned to: people keep their number when they change carrier, so any one number may have moved since.

Carriers holding the most 312 numbers
CarrierKindShare
AT&TLandline39%
T-MobileMobile12%
AT&T MobilityMobile9%
Verizon WirelessMobile7%
Level 3Cable, VoIP, other5%
Verizon BusinessCable, VoIP, other5%

An area code says where a number was issued, not where the caller is: people keep their numbers when they move, and caller ID can be set to show any number, which the FCC calls spoofing. If a call you did not expect asks for money or personal details, the FCC advises hanging up and calling the company back on a number you look up yourself. Unwanted calls can be reported to the FTC at ReportFraud.ftc.gov.

Places in area code 312

The 3 places with a telephone rate centre of their own using 312, largest first. Each links to its ZIP codes.

Places in area code 312
PlaceZIP codesPopulation
Chicago, IL 84 2,711,226
Wheeling, IL 1 38,433
Hinsdale, IL 2 17,175

Nearby places using 312

These places have no rate centre of their own in NANPA's records; the nearest one uses 312. Near an area-code boundary that can be wrong for part of a town.

ZIP codes in area code 312

91 ZIP codes in 7 towns, by the town each is mailed to, largest first. Each links to its own page.

Where 312 numbers are issued

NANPA's rate centres with the most 312 prefixes (each prefix is 10,000 numbers), under NANPA's own abbreviated names.

Rate centres using area code 312
Rate centrePlacePrefixes
CHICGOZN01 Chicago 746
WHEELING Wheeling 12
HINSDALE Hinsdale 11
LA GRANGE La Grange 8
NORTHBROOK Northbrook 3
ROSELLE Roselle 2

Counties

The counties of its ZIP codes, most residents first, with how many of its ZIP codes each has.

Which code covers where you are now? What area code am I in? answers from your location.

Questions about area code 312

Where is area code 312?

Area code 312 is in Illinois. It covers Chicago, Wheeling, Westmont and 5 other places: 91 ZIP codes in Cook and DuPage counties.

What ZIP codes are in area code 312?

91 ZIP codes, by the town each is mailed to: Chicago (84, 60601 to 60701), Wheeling (60090), Westmont (60559), Hinsdale (2, 60521 to 60522) and 3 more towns. The full list is on this page.

What time zone is area code 312 in?

Central time.

Is a 312 number a mobile or a landline?

It can be either. 28% of 312 numbers are assigned to mobile carriers and 39% to local phone companies (NANPA, 2026-10-10); the rest are with cable, internet-calling, business and paging carriers. A number keeps its area code when it moves to another carrier.

What area codes overlay 312?

872. They cover the same area as 312, so a new number there can be given any of them.

Does a 312 number mean the caller is in Illinois?

Not necessarily. An area code says where the number was first issued. People keep their numbers when they move or switch carriers, and calling software can show any number, so a 312 call can come from anywhere.

Other area codes in Illinois

All 17 Illinois area codes, by area, with the cities each covers

Source: NANPA NPA database, central office code and thousands-block assignments, 2026-10-10. Places are matched to NANPA's rate centres by name; see sources.

Cite this page

zipcodes.pro. “Area code 312.” Data release 2026-10-12. Retrieved 2026-10-20. https://zipcodes.pro/area-code/312

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