Area code 423

Area code 423 Chattanooga, Tennessee

Area code 423 is in Tennessee, with numbers assigned in Chattanooga, Johnson City, Bristol and 59 more places. It’s 12:11 AM there now.

State: Tennessee8 area codes in Tennessee
Time zone: Eastern and CentralSplit between 2 zones
Exchanges: 76462 places
Overlay: 729Same area, 10-digit dialing

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Where area code 423 is

Numbers in 423 are assigned to 62 places in 27 counties: Hamilton County, Sullivan County, Carter County, Washington County, Hawkins County, McMinn County, plus 21 more.

Chattanooga has the most, 24% of the exchanges; the rest are spread across 61 other places.

Chattanooga183
Johnson City67
Bristol38
Cleveland33
Kingsport32
Morristown28
Athens22
Greeneville20
La Follette16
Newport15
Elizabethton13
Rogersville12
Blountville10
Benton9
Charleston9
Bulls Gap9
Sweetwater9
Erwin8
Soddy-Daisy8
Dayton8
Madisonville8
Oneida7
Pikeville7
South Pittsburg7

Phone companies in 423

764 blocks of numbers in 423 are held by 48 phone companies. The most belong to AT&T (119), Lumen (CenturyLink) (85) and AT&T Mobility (80).

A mix: about 32% wireless, 35% local phone and cable and 33% other carriers, including internet phone services.

A block’s holder is the company it was first assigned to; numbers can move to other carriers since.

History and overlays

423 went into service in 1995, added to the area of 615.

729 (since 2025) shares the same area, so a new number there can get any of these codes and local calls are dialed with all 10 digits.

99 new exchanges were assigned since 2021, the latest in September 2026.

Calling 423

423 spans the Eastern and Central time zones: right now it’s 12:11 AM Eastern and 11:11 PM Central. Check which side of the line someone is on before calling early or late.

From elsewhere in the U.S., dial 1, 423 and the 7-digit number; inside the area, all 10 digits too.

Nearby area codes

Tennessee has 8 area codes: 423, 615, 629, 729, 731, 865, 901 and 931.

From the North American Numbering Plan Administrator’s area code and exchange records (10/22/2026) and U.S. Census place and county names. Places and companies are where number blocks were assigned, not where anyone lives or which carrier a number uses today.

Map of the 423 area code

Map of the 423 area code around Chattanooga, Johnson City and Bristol, Tennessee.

Interactive map © OpenStreetMap contributors

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Questions about 423

Where is area code 423?

In Tennessee, covering Chattanooga, Johnson City and Bristol and other places across 27 counties.

What time zone is 423 in?

Two: Eastern and Central. Right now it’s 12:11 AM Eastern and 11:11 PM Central.

Is 423 an overlay?

Yes. 729 serves the same area, so dial all 10 digits for local calls.

Which phone companies have 423 numbers?

48 companies hold blocks; the most belong to AT&T, Lumen (CenturyLink) and AT&T Mobility. About 32% of blocks are wireless.

Is 423 running out of numbers?

Not on record. 99 new exchanges have been assigned since 2021.