636 Area Code — Missouri
636 is a North American Numbering Plan area code for Missouri, the United States. It covers about 1,007,929 people in 62 towns and 72 ZIP codes, including Saint Charles, O Fallon and Ballwin.
| Field | Value |
|---|---|
| Area code | 636 |
| Country | United States (+1) |
| State / province | Missouri |
| Type | Standalone (no other NANP code covers the same towns) |
| Time zone | Central |
| Population covered | 1,007,929 |
| Towns covered | 62 |
| ZIP codes | 72 |
| Approx. centre | 38.605, -90.727 |
Where area code 636 is used
Area code 636 is assigned to Missouri, the United States, inside the North American Numbering Plan. Numbers in the code are written (636) NXX-XXXX at home and +1 636 NXX-XXXX when dialled from outside Canada and the United States. Since the NANP moved to 10-digit dialling you must always include the area code, even for a local call.
Towns and cities in area code 636
The 62 towns below are the largest in the 636 footprint, ranked by population. Every one of them links to its own page with the full list of area codes and ZIP codes for that town.
| Town | County | Population | ZIP codes |
|---|---|---|---|
| Saint Charles | St. Charles County | 141,951 | 4 |
| O Fallon | St. Charles County | 101,735 | 2 |
| Ballwin | St. Louis County | 91,586 | 4 |
| Saint Peters | St. Charles County | 74,962 | 1 |
| Chesterfield | St. Louis County | 63,022 | 3 |
| Wentzville | St. Charles County | 51,330 | 1 |
| Fenton | Jefferson County | 45,354 | 2 |
| Arnold | Jefferson County | 34,478 | 1 |
| Lake Saint Louis | St. Charles County | 29,725 | 1 |
| Imperial | Jefferson County | 28,712 | 1 |
| Troy | Lincoln County | 27,731 | 1 |
| Washington | Franklin County | 23,258 | 1 |
Counties covered
| County | ZIP codes |
|---|---|
| Jefferson County | 18 |
| St. Charles County | 16 |
| St. Louis County | 13 |
| Franklin County | 10 |
| Warren County | 7 |
| Lincoln County | 6 |
| Montgomery County | 1 |
| Callaway County | 1 |
Nearby area codes
How to dial area code 636
- Within North America: 636 + 7-digit number (636-NXX-XXXX). The leading 1 is optional on a mobile phone and required on most landlines for long-distance.
- From abroad: your country's international prefix, then 1, then 636, then the 7-digit number — for example 00 1 636 NXX-XXXX from most of Europe.
Frequently asked questions
What area code is 636?
636 is a North American Numbering Plan area code assigned to Missouri, the United States. It covers about 1,007,929 people in 62 towns.
Is 636 a US or Canadian area code?
636 is a United States area code. Canada and the United States share the +1 country code, so both are part of the same numbering plan.
What time zone is area code 636 in?
Area code 636 is in the Central time zone.
Do I have to dial 10 digits?
Yes. Every NANP call now requires the area code plus the seven-digit number, even for a local call.