Area codes in Longmont, Colorado
Longmont, Colorado uses 3 area codes — 303, 720 and 983. The main Longmont area code is 303.
Area codes serving Longmont
Phone numbers in Longmont are written as ten digits — for example (303) 555-0190 — and fall in the Mountain Time zone.
How Longmont came to have 3 area codes
The original Longmont area code is 303, in service since 1947. As the area ran low on available numbers, overlay codes were added over the same region for new phone lines: 720 (1998) and 983 (2022). Existing numbers kept their original code — an overlay never forces anyone to change their number — which is why Longmont now uses all 3 codes and every local call is dialed with ten digits.
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Nearby cities
- Boulder area codes
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Frequently asked questions
What is the area code for Longmont?
The main area code for Longmont, Colorado is 303. Longmont is now served by 3 area codes in total: 303, 720, 983.
How many area codes does Longmont have?
Longmont has 3 area codes: 303, 720, 983.
Why does Longmont have more than one area code?
As Longmont used up the numbers available in its original area code (303, 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 Longmont number?
Dial all 10 digits — the area code (303 or 720 or 983) 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.