Area code 406: Montana
Area code 406 is a US state area code for Montana, on Mountain Time. It has 754 prefixes in service across 260 rate centers, the largest being Billings, Missoula and Helena. NANPA lists no overlay code for it. Local calls there take 10 digits.
Local time in area code 406
America/Denver
Prefixes in service
754 of 792 possible
260 rate centers
Area code 406 facts
| Location | Montana, United States |
|---|---|
| Time zone | Mountain Time |
| Overlays | None |
| In service since | 1947, when the plan began |
| Local calls | 10 digits; toll calls 1 + 10 digits |
| Carrier | Not shown. An area code is where a number was issued; numbers port between carriers. Check line type |
Which cities and towns use area code 406?
NANPA records each prefix against a rate center, the local billing area a number belongs to, usually named after its main town. These are the 406 rate centers with the most prefixes in service. 248 smaller ones aren't listed.
| Rate center | Prefixes |
|---|---|
| Billings | 72 |
| Missoula | 47 |
| Helena | 38 |
| Great Falls | 37 |
| Bozeman | 32 |
| Kalispell | 25 |
| Butte | 17 |
| Miles City | 10 |
| Sidney | 9 |
| Livingston | 8 |
| Lewistown | 8 |
| Hamilton | 8 |
Source: NANPA central office code assignments, file dated 10/17/2026. Each prefix holds up to 10,000 numbers.
How do I dial a 406 number?
NANPA's dialling plan for 406: local calls inside the code take 10 digits, toll calls 1 + 10 digits. From another area code, dial 1 first. From abroad, use +1. The examples use 555-0147, from a range reserved for fictional numbers.
| Local call inside 406 | 406-555-0147 |
|---|---|
| From another US or Canadian area code | 1-406-555-0147 |
| From outside North America | +1 406 555 0147 |
| E.164, for CRMs and SMS tools | +14065550147 |
When did area code 406 start?
Area code 406 is one of the original codes NANPA lists from 1947. It has no overlay, so every number in its area still starts with it.
Tools for 406 numbers
- Area code lookup
Look up any code or a whole list of numbers, or find the codes for a state or city.
- Area code time zone
Local time for a list of numbers, with a callable-now flag.
- NPA-NXX lookup
Rate center and state for one prefix, a level below the area code.
- TCPA calling hours checker
Whether it's inside the federal 8 a.m. to 9 p.m. calling window there now.
Next step
A 406 number tells you where it was issued, not what it is now.
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Area code 406 questions
- What state is area code 406?
- Area code 406 is in Montana, United States. Its largest rate centers by number of prefixes are Billings, Missoula, Helena, Great Falls and Bozeman.
- What time zone is area code 406 in?
- Mountain Time.
- Does area code 406 have an overlay?
- Not as of NANPA's file dated 10/16/2026. Every number in its area uses 406.
- When did area code 406 start?
- Area code 406 is one of the original codes NANPA lists from 1947.
- Is a 406 number a cell phone or a landline?
- The area code can't tell you. In the US and Canada mobiles, landlines and VoIP lines share area codes and prefixes, and numbers move between carriers and line types. Only a live line-type lookup answers it for one number.
- How many phone numbers does area code 406 have?
- 754 of its 792 possible prefixes are in service, and each prefix holds up to 10,000 numbers. That counts prefixes assigned to carriers, not numbers in use.
Sources
Location, overlays, in-service date and dialling plan: NANPA NPA database, file dated 10/16/2026. Prefixes and rate centers: NANPA central office code assignments, 10/17/2026. Time zones mapped to the IANA time zone database. By the SimpleVerifier Team; how we build these pages.