331 Area Code
Covers Naperville and nearby communities in Illinois.
(331) 555-0142Area code 331 map
Interactive coverage map for area code 331, centered on Naperville, Illinois
41.7859, -88.1473
Open in OpenStreetMapArea code 331 coverage map — centered on Naperville. Shaded area shows the approximate reach around the primary city.
Area code 331 is a telephone area code in Illinois, anchored on Naperville. It reaches roughly 610,000 people across places such as Naperville, Bolingbrook, Wheaton, Downers Grove and more. The region observes Central time, so a number like (331) 555-0142 is on that clock right now. On the ground it spans Dupage, Will, Cook and nearby counties. It shares its territory with the overlay codes 630, 773, 872, which sit on the exact same map. Because the 331 region uses more than one area code, you must dial all ten digits — area code included — even for a local call. You do not, however, need to dial a leading 1 for calls within the US and Canada. Keep reading for the current local time in Naperville, a map of the 331 coverage area, the places it reaches, nearby and overlay codes, and how to tell a real 331 call from a scam.
Cities covered by 331
Cities & neighborhoods
- Naperville
- Bolingbrook
- Wheaton
- Downers Grove
- Elmhurst
- Lombard
- Bartlett
- Carol Stream
- Streamwood
- Hanover Park
- Addison
- Batavia
- Bensenville
- Bloomingdale
- Darien
- Glen Ellyn
- Glendale Heights
- Lisle
- North Aurora
- Roselle
- Saint Charles
- Villa Park
- West Chicago
- Westmont
- Woodridge
Nearby & overlay area codes
Overlay codes (same area)
These share 331’s geography — a number in either code can be on the same street.
Neighboring codes
Codes for adjacent regions and metros.
Is a call from 331 a scam?
Area code 331 serves Naperville and the surrounding area, so most calls are ordinary local and business traffic. As everywhere, spam and robocalls do use 331 numbers, frequently by spoofing a local-looking caller ID to boost pickup rates. The area code itself tells you nothing about who is really calling, so judge the call by what's said, not the number.
Red flags to watch for
- Pressure to act right now, or threats of arrest, fines, or service being cut off.
- Requests to pay with gift cards, wire transfer, crypto, or a payment app.
- Asking for passwords, one-time codes, your SSN, or full card/bank numbers.
- A robocall or recording, or a number that won’t let you call back.
When unsure, hang up and call the organization back on a number you look up yourself.
Calling a 331 number from abroad
Every 331 number is a US/Canada +1 number. From a mobile anywhere, the simplest approach is to dial it in international format:
+1 331 555-0142If your phone can’t dial the +, replace it with your country’s exit code, then 1, then the number:
- UK, Germany, France & most of Europe
00 1 331 555-0142 - Australia
0011 1 331 555-0142 - Japan
010 1 331 555-0142 - Mexico
00 1 331 555-0142
Within the US and Canada you don’t need any of this — just dial the ten digits 331 555-0142.
Reverse phone lookup
Check any US or Canada number to see whether it's a working line, which carrier it sits on, whether it's mobile, landline or VoIP, and roughly where it's registered.
Shows carrier, line type and location. Owner name isn't available here.
Results are for personal, informational use only and may not be used for employment, credit, housing or tenant-screening decisions.
Area code 331: frequently asked questions
Where is the 331 area code located?
The 331 area code is located in Illinois, centered on Naperville. It covers Dupage, Will, Cook, Kane and nearby communities including Naperville, Bolingbrook, Wheaton, Downers Grove, Elmhurst, Lombard.
What time zone is 331 in?
Area code 331 is in the Central time zone (UTC-6 (CST) / UTC-5 (CDT)). You can see the exact current local time for Naperville on the live clock above.
What cities use area code 331?
Cities and areas that use 331 include Naperville, Bolingbrook, Wheaton, Downers Grove, Elmhurst, Lombard. Its primary city is Naperville, IL.
Do I need to dial 1 before 331?
For calls within the US, you do not need to dial a leading 1, but you do need all ten digits: 331 plus the seven-digit number. The 331 area requires ten-digit dialing because more than one area code serves it.
Is 331 a toll-free or scam number?
No — 331 is a normal geographic area code for Naperville, not a toll-free code (toll-free codes are 800, 833, 844, 855, 866, 877 and 888). A 331 number is not inherently a scam, but the code can be spoofed. See the spam-call section above for how to tell.
What are the overlay area codes for 331?
Area code 331 is overlaid by 630, 773, 872, meaning those codes cover the same geographic area.