Area codes in Thousand Oaks, California

Thousand Oaks, California uses 2 area codes — 805 and 820. The main Thousand Oaks area code is 805.

Area codes serving Thousand Oaks

Phone numbers in Thousand Oaks are written as ten digits — for example (805) 555-0190 — and fall in the Pacific Time zone.

How Thousand Oaks came to have 2 area codes

The original Thousand Oaks area code is 805, in service since 1957. As the area ran low on available numbers, an overlay code was added over the same region for new phone lines: 820 (2018). Existing numbers kept their original code — an overlay never forces anyone to change their number — which is why Thousand Oaks now uses all 2 codes and every local call is dialed with ten digits.

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Frequently asked questions

What is the area code for Thousand Oaks?

The main area code for Thousand Oaks, California is 805. Thousand Oaks is now served by 2 area codes in total: 805, 820.

How many area codes does Thousand Oaks have?

Thousand Oaks has 2 area codes: 805, 820.

Why does Thousand Oaks have more than one area code?

As Thousand Oaks used up the numbers available in its original area code (805, in service since 1957), additional "overlay" codes were added over the same area so new phone numbers could keep being assigned.

How do you dial a Thousand Oaks number?

Dial all 10 digits — the area code (805 or 820) followed by the 7-digit local number. From abroad, dial +1, then the area code and number.

Sourced from the official NANPA (North American Numbering Plan Administrator) numbering database, current as of August 2, 2026. Refreshed monthly.