Area Code
Illinois, United States
Local Time
4:29 AM
Central Time
Area Code
331
State / Province
Illinois
Country
United States
Time Zone
Central Time
Area code 331 covers 22 rate centers across Illinois. Rate centers are geographic areas used by telephone companies to determine local calling boundaries.
Use the E.164 format for clickable phone links (RFC 3966):
<a href="tel:+13315550100">+13315550100</a><a href="tel:+13315550199">+13315550199</a>Area code 331 is a North American Numbering Plan (NANP) telephone area code assigned to Illinois, United States. It is one of 16 area codes serving Illinois. As population and demand for phone numbers grew, the region was divided into multiple numbering plan areas to avoid exhausting the available 7-digit number pool.
Yes. 331 is an active North American Numbering Plan (NANP) area code, currently assigned to Illinois, United States. It is safe to answer or dial calls using this area code.
Area code 331 covers 22 rate centers across Illinois. Communities served include Aurora, Bartlett, Bensenville, Big Rock, Downers Grove, and 17 more localities. Rate centers are the geographic building blocks telephone carriers use to determine local calling boundaries and to assign numbers when a business or individual requests a phone number in a specific city.
All numbers in the 331 area code observe Central Time (IANA timezone: America/Chicago). Central Time is UTC−6 in winter (CST) and UTC−5 in summer (CDT). When placing a call to a 331 number from a different time zone, check the current local time above to avoid calling outside of business hours.
From within Illinois, dial the 7-digit local number directly if calling within the same rate center, or dial 1 + 331 + 7-digit number for long-distance calls within North America. From outside the US or Canada, dial your country's international exit code followed by 1 331 XXX XXXX. The country code for both the United States and Canada in NANP is +1.
Format 331 numbers using E.164 notation as required by RFC 3966: prefix with +1 and omit dashes and parentheses (e.g., +13315550100). This format ensures tel: links work correctly on all mobile browsers and VoIP apps. See the tel: URI formatting guide for complete examples.