| Area Code | 406 |
| State | Montana |
| Current Time in Area Code 406 | 406> MDT |
| Timezone | Mountain Daylight Time |
| Regional Market Area | Billings Area Butte-Bozeman-Helena Area Great Falls Area Minot-Bismark-Dickinson Area Missoula Area Rapid City Area Spokane Area |
| Metro Area(s) | Billings, MT Bozeman, MT Butte-Silver Bow, MT Great Falls, MT Helena, MT Kalispell, MT Missoula, MT |
| Population (2020) | 1084225 |
| Adjacent Area Codes | 208,236,250,306,307,368,403,474,587,605,639,672,701,778,825 |