Where is the 312 area code?

Area code 312 covers Illinois, on Central Time.

What time zone is area code 312 in?

Numbers in the 312 area code sit in Central Time.

Is 312 a toll-free or scam area code?

No. 312 is a geographic North American Numbering Plan area code assigned to Illinois. Toll-free numbers use 800, 833, 844, 855, 866, 877 and 888. A call from 312 can still be spoofed, so treat unexpected calls with the usual caution.

Area code lookup

312 area code

Where the 312 area code is, which cities and counties it serves, the local time zone and the overlay codes dialled alongside it.

State: IL
Codes in state: 17
Overlays & neighbours: 16
Time zone: Central Time

Quick answer

Area code 312 is a geographic area code assigned to Illinois under the North American Numbering Plan. Illinois observes Central Time, and the state also holds 16 other area codes: 217, 224, 309, 331, 447, 464, 618, 630, 708, 730, 773, 779, 815, 847, 861, 872.

Largest cities in Illinois

The largest places in Illinois. Each links to its full local profile: population, income, housing and sales tax.

City	Population
Chicago city	2,707,648
Aurora city	179,867
Joliet city	149,785
Naperville city	149,424
Rockford city	147,649
Elgin city	114,106
Springfield city	113,714
Peoria city	112,126
Waukegan city	88,919
Champaign city	88,822
Cicero town	83,223
Bloomington city	78,703

All Illinois cities All Illinois ZIP codes Illinois sales tax

Related area codes

Codes that share or border the same calling area.

312 area code FAQ

The questions people ask about this code.

Where is area code 312?

312 is a geographic area code in Illinois.

What time is it in the 312 area code?

312 observes Central Time.

Is 312 a scam area code?

No — it is a normal geographic code, not a toll-free or premium-rate prefix. Caller ID can be spoofed on any code, so verify unexpected callers before sharing information.

Sources & transparency

North American Numbering Plan Administrator (NANPA) area code assignments — area code to geography mapping and overlay relationships
US Census Bureau, American Community Survey 2019-2023 5-year estimates — city, county and ZIP code geography

Last reviewed August 2026. Figures are published for reference and can change; verify with the source agency before filing or contracting. How we build and check this data.