Area codes in Simi Valley, California
Simi Valley, California uses 2 area codes — 805 and 820. The main Simi Valley area code is 805.
Area codes serving Simi Valley
Phone numbers in Simi Valley are written as ten digits — for example (805) 555-0190 — and fall in the Pacific Time zone.
How Simi Valley came to have 2 area codes
The original Simi Valley 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 Simi Valley 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 Simi Valley?
The main area code for Simi Valley, California is 805. Simi Valley is now served by 2 area codes in total: 805, 820.
How many area codes does Simi Valley have?
Simi Valley has 2 area codes: 805, 820.
Why does Simi Valley have more than one area code?
As Simi Valley 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 Simi Valley 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.