Illinois · Central Time
Chicago, IL Area Codes
Chicago is served by 3 area codes (312, 773, 872). Here's which is original, which are overlays, and how to pick one for a new local number.
Last updated June 5, 2026
Area codes serving Chicago
Chicago sits in Illinois, part of the Midwest region and the Central Time zone. Its numbers are spread across an overlay of 3 codes that all cover the same ground: 312, 773, 872.
The original code is 312. As the area ran low on numbers, regulators added overlay codes on top instead of splitting the city, so longtime residents kept their numbers while new lines received a newer code.
How to pick an area code for a new number
When you activate a new line in Chicago, the carrier assigns whichever code has numbers available — you usually can't choose. If a specific code matters to you (for example the prestige of 312), ask the carrier whether any blocks remain, or request a number transfer. All codes here dial identically and cost the same.
Dialing in Chicago
Because Chicago is an overlay area, 10-digit dialing is mandatory: always dial the area code plus the seven-digit number, even for a neighbor. See 10-digit dialing and overlay area codes for the background. For every code in Illinois, visit the Illinois area codes page.
Quick answers
Chicago area code FAQ
What area codes does Chicago use?
Chicago, IL is served by 3 area codes: 312, 773, 872.
Which is the original Chicago area code?
312 is the original/primary code for Chicago; the others are overlays added later for more numbers.
Do I need to dial the area code in Chicago?
Yes. With multiple overlapping codes, 10-digit dialing is required for every call in this area.