The seat of Montgomery County and one of the principal cities of the Washington, D.C. suburbs, Rockville is a diverse, fast-growing hub along the I-270 biotech corridor. It is covered by the 301 code and its overlay. This guide breaks down Rockville’s 301 and 240 codes, the required 10-digit dialing, major ZIP codes, and local scam warnings.
Rockville Area Codes at a Glance
| Detail | Information |
|---|---|
| Primary Area Code(s) | 301 |
| Overlay Area Code(s) | 240 |
| Time Zone | Eastern Time (ET) – EST / EDT |
| Major County | Montgomery County |
| Region | DC Suburbs (Montgomery County) |
| Dialing Format | 10-digit dialing required |
Area Code Breakdown & Regional Mapping
301 – Western MD & DC Suburbs Code
Area code 301 is one of the original 1947 codes and covers the Washington, D.C. suburbs and Western Maryland, including Rockville, Gaithersburg, and Bowie. It is Rockville’s primary code and anchors Montgomery County.
240 – Western MD & DC Suburbs Overlay
Area code 240 is the 1997 overlay for the 301 region, sharing the same DC-suburbs and western-Maryland geography. Many newer Rockville lines carry a 240 prefix, fully local to existing 301 numbers.
Neighborhoods & Local Coverage
Rockville’s 301/240 codes cover a city anchored by the revitalized Rockville Town Center, a walkable district of shops, restaurants, and the Montgomery County government complex. The historic core near the courthouse — where author F. Scott Fitzgerald is buried — sits alongside newer transit-oriented development around the Metro station.
Beyond the center, the same codes reach the master-planned King Farm and Fallsgrove communities, the Twinbrook and East Rockville neighborhoods, and the biotech and life-sciences campuses lining the I-270 corridor. As part of the DC suburbs, Rockville shares the 301/240 codes with neighboring Gaithersburg and the rest of Montgomery County.
Local Dialing Rules & International Format
Rockville and the 301 region have required 10-digit dialing since the 240 overlay launched — always dial the area code plus the 7-digit number. Baltimore to the northeast uses a separate complex, 410/443/667.
Rockville is in the Eastern Time Zone (EST/EDT), like all of Maryland. To call the city from outside the United States, dial your country’s exit code, then the U.S. country code +1, followed by the 10-digit number (for example, +1 301 XXX-XXXX). From inside the U.S. and Canada, simply dial 1 before the 10-digit number for long-distance calls.
Major ZIP Codes Covered
The 301 service area spans many of Rockville’s core ZIP codes, including 20850, 20851, 20852, and 20853.
Spam & Scam Call Warnings in Rockville
Rockville residents report neighbor-spoofing robocalls faking a local 301 prefix, plus fake utility-shutoff threats from callers posing as Pepco. Tech-support and fake-investment scams also target the area’s affluent, professional population.
| Scam Type | What to Watch For |
|---|---|
| Neighbor Spoofing | Calls that mimic a local 301 prefix to look familiar. |
| Utility / Toll Scams | Threats to shut off power or demand toll payment via gift cards. |
| IRS / Government | Robocalls claiming legal action — agencies never call to demand instant payment. |
Red flag: Any caller who pressures you to pay immediately with gift cards, wire transfers, or cryptocurrency is almost certainly running a scam. Hang up and verify through an official number.
↑ See the complete list of All US Area Codes by State for every code across the country.
Nearby & Related Maryland Cities
Frequently Asked Questions
What area code is Rockville, MD?
Rockville uses area code 301 and its overlay 240, shared across the DC suburbs and Western Maryland.
Does Rockville have the same area code as Gaithersburg?
Yes. Rockville, Gaithersburg, and the rest of Montgomery County all use 301/240.
Do I need to dial 10 digits in Rockville?
Yes. With the 240 overlay active, all local calls in the 301 region require 10-digit dialing.
What time zone is Rockville in?
Rockville observes Eastern Time (EST/EDT), like all of Maryland.
Stay Safe & Explore More
- Verify an unknown caller in our Scam Alerts directory.
- Comparing nationwide numbers? See our Toll-Free Numbers guides.