Area codes in Rockville, Maryland
Rockville, Maryland uses 3 area codes — 301, 240 and 227. The main Rockville area code is 301.
Area codes serving Rockville
Phone numbers in Rockville are written as ten digits — for example (301) 555-0190 — and fall in the Eastern Time zone.
How Rockville came to have 3 area codes
The original Rockville area code is 301, in service since 1947. As the area ran low on available numbers, overlay codes were added over the same region for new phone lines: 240 (1997) and 227 (2023). Existing numbers kept their original code — an overlay never forces anyone to change their number — which is why Rockville now uses all 3 codes and every local call is dialed with ten digits.
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Nearby cities
- Silver Spring area codes
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Frequently asked questions
What is the area code for Rockville?
The main area code for Rockville, Maryland is 301. Rockville is now served by 3 area codes in total: 301, 240, 227.
How many area codes does Rockville have?
Rockville has 3 area codes: 301, 240, 227.
Why does Rockville have more than one area code?
As Rockville used up the numbers available in its original area code (301, in service since 1947), additional "overlay" codes were added over the same area so new phone numbers could keep being assigned.
How do you dial a Rockville number?
Dial all 10 digits — the area code (301 or 240 or 227) 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.