303 area code
Denver area, Mountain Time.Area code 303 covers Denver, Longmont, Fort Lupton and 10 more places in Colorado, on Mountain Time. 720 and 983 cover the same area.
Right now in Denver
Mountain Time (MST, UTC-7; MDT, UTC-6 in summer)
Calling hours: Every day, 8 AM to 9 PM (the federal rule)
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Where 303 numbers come from
Numbers are issued by rate center, a billing area named for its main town. 303 has 13. Each one's share is how many 303 numbers start there. Its biggest metro area is Denver-Aurora-Centennial, CO.
- Denver94%
- Longmont2%
- Fort Lupton1%
- Deckers<1%
Also: Keenesburg, Georgetown, Allenspark-Lyons, Hudson, Deer Trail, Strasburg, Bennett, Byers, Roggen
Share of exchanges (blocks of 10,000 numbers). Source: NANPA rate center and exchange reports, November 10, 2026
When can you call a 303 number?
Sales calls to homes and cell phones have legal hours, set by the federal rule. Hold every 303 number to them, since you can't tell a work line from a personal cell.
What applies to 303Every day, 8 AM to 9 PM
- Federal (TCPA and FTC rule)Every day, 8 AM to 9 PMCalls to residential and mobile numbers. Most calls to businesses are exempt from the FTC's rule.47 CFR 64.1200(c)(1); 16 CFR 310.4(c) (opens in a new tab)
Local time comes from the area code, not from where the person is today. Mobiles keep their number when they move. Calling hours here are a guide, not legal advice. Every state's calling hours, with sources
303 and 720 and 983
303 is one of the original area codes from 1947, and 719 and 970 were later split off from it. 303, 720 and 983 cover the same area, so new numbers can get any of them and neighbors can have different area codes. 303 holds 49% of the area's exchanges, about as many as 720. Local calls take all 10 digits.
- 1947303 starts
- 1988719 split off
- 1995970 split off
- 1998720 overlay
- 2022983 overlay
Source: NANPA area code database
Other Colorado area codes
All Colorado area codesCalling a list of 303 numbers?
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303 area code FAQ
What area code is 303?
303 is a Colorado area code for Denver, Longmont, Fort Lupton, Deckers and 9 more places.
What time zone is the 303 area code in?
Mountain Time (MST, UTC-7; MDT, UTC-6 in summer).
Is 720 the same as 303?
Same area, different code. 303, 720 and 983 cover the same area (an overlay), so new numbers can get any of them and local calls take all 10 digits.
What are the calling hours for 303 numbers?
Every day, 8 AM to 9 PM, local time, under the federal rule.
When did the 303 area code start?
In 1947: it's one of the original area codes.
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