Area Code 331: Illinois, Illinois
331 is a telephone area code serving Illinois. It is part of the North American Numbering Plan and is dialed with the country code +1.
Numbers beginning with 331 are located in Illinois, United States (NANP region: Chicago).
How to Dial Area Code 331
| Calling from | What to dial |
|---|---|
| Anywhere in the US or Canada | 1 331 XXX-XXXX (10-digit dialing: 331 + 7-digit number) |
| Local call inside the same area code | 7-digit number in most areas; 10 digits where an overlay code is active |
| From the UK or Europe | 00 1 331 XXX XXXX |
| From Australia | 0011 1 331 XXX XXXX |
| From a mobile phone anywhere | +1 331 XXX XXXX |
Whatever country you are calling from, the + symbol replaces the exit code. Save the contact as +1 331 XXXXXXX and it will dial correctly from any phone in the world.
Time Zone for Area Code 331
Calls to a 331 number ring in the America/Chicago time zone, standard offset UTC-06:00. Daylight saving time applies here, so the offset moves forward one hour from March to November.
Other Area Codes in Illinois
These codes also serve Illinois. Area codes are assigned by the North American Numbering Plan Administration (NANPA).
| Area Code | Cities / Coverage |
|---|---|
| 217 | Springfield, Champaign |
| 224 | Chicago North Suburbs (overlay) |
| 309 | Peoria, Moline |
| 312 | Chicago (downtown) |
| 464 | Chicago South Suburbs (overlay for 708) |
| 618 | East St. Louis, Carbondale |
| 630 | Chicago West Suburbs |
| 708 | Chicago South Suburbs |
| 730 | Southern Illinois (overlay for 618) |
| 773 | Chicago (outer) |
| 815 | Rockford, Joliet |
| 847 | Chicago North Suburbs |
| 872 | Chicago (overlay) |
See all 14 area codes in Illinois →
Frequently Asked Questions
Where is area code 331?
Area code 331 is in Illinois, United States. It covers Chicago West Suburbs (overlay).
What time zone is area code 331 in?
Area code 331 rings in the America/Chicago time zone (UTC-06:00 standard).
Do I need to dial 1 before area code 331?
Yes, for a long-distance call inside the US and Canada you dial 1 first, then 331, then the seven-digit number. The 1 is the North American long-distance trunk prefix — it is not the country code. From outside North America you dial your exit code then 1 then 331.
Is area code 331 toll-free?
No. 331 is a standard geographic area code, so normal long-distance rates apply unless your plan includes them. Toll-free NANP codes are 800, 833, 844, 855, 866, 877 and 888.