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Area code 312

Area code 312 Chicago, Illinois

Area code 312 is one of the original 1947 area codes, in Illinois, with numbers assigned in Chicago, Wheeling, Hinsdale and 3 more places. It’s 11:13 PM there now.

State
Illinois17 area codes in Illinois
Time zone
Central11:13 PM there now
Exchanges
7846 places
Overlay
872Same area, 10-digit dialing
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Where area code 312 is

Numbers in 312 are assigned to 6 places in 3 counties: Cook County, DuPage County and Lake County.

Chicago holds most of them: 95% of the exchanges.

  • Chicago748
  • Wheeling12
  • Hinsdale11
  • La Grange8
  • Northbrook3
  • Roselle2

Phone companies in 312

784 blocks of numbers in 312 are held by 33 phone companies. The most belong to AT&T (334), AT&T Mobility (82) and T-Mobile (71).

A mix: about 27% wireless, 44% local phone and cable and 30% other carriers, including internet phone services.

A block’s holder is the company it was first assigned to; numbers can move to other carriers since.

History and overlays

312 has been in service since 1947, when the first North American area codes were set up.

872 (since 2009) shares the same area, so a new number there can get any of these codes and local calls are dialed with all 10 digits.

9 new exchanges were assigned since 2021, the latest in January 2026.

Calling 312

It’s 11:13 PM Central time in 312 right now.

From elsewhere in the U.S., dial 1, 312 and the 7-digit number; inside the area, all 10 digits too.

Nearby area codes

Illinois has 17 area codes: 217, 224, 309, 312, 331, 447, 464, 618, 630, 708, 730, 773, 779, 815, 847, 861 and 872.

From the North American Numbering Plan Administrator’s area code and exchange records (10/22/2026) and U.S. Census place and county names. Places and companies are where number blocks were assigned, not where anyone lives or which carrier a number uses today.

Map of the 312 area code

Map of the 312 area code around Chicago, Wheeling and Hinsdale, Illinois.

Interactive map © OpenStreetMap contributors

Cities on the map

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Questions about 312

Where is area code 312?

In Illinois, covering Chicago, Wheeling and Hinsdale and other places across 3 counties.

What time zone is 312 in?

Central time. It was 11:13 PM there when this page loaded.

Is 312 an overlay?

Yes. 872 serves the same area, so dial all 10 digits for local calls.

Which phone companies have 312 numbers?

33 companies hold blocks; the most belong to AT&T, AT&T Mobility and T-Mobile. About 27% of blocks are wireless.

Is 312 running out of numbers?

Not on record. 9 new exchanges have been assigned since 2021.