🇺🇸USA State Guide: Colorado

Colorado Area Codes
303, 720, 970 & 719

Need to call Denver, Aspen, or Colorado Springs? Connect instantly to any Colorado number. Whether it's a business in the Tech Center or a resort in the Rockies, make HD calls directly from your browser.

How to Dial
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How to Call Colorado Step-by-Step

Calling Colorado follows the standard North American Numbering Plan (NANP).

1

Exit Code

Dial 00 (if in Europe) or your country's specific exit code.
(Or just use + on mobile/VoIP)

2

US Country Code

Dial 1. This is the country code for the United States, Canada, and parts of the Caribbean.

3

Area Code + Number

Dial the 3-digit Colorado area code (e.g., 303) followed by the 7-digit phone number.

Mandatory 10-Digit Dialing

Colorado has multiple "overlay" area codes (e.g., 303 and 720 both cover Denver). This means you must always dial the full 10 digits (Area Code + Phone Number), even for local calls within the same city.

Example Format
+1 (303) 555-0123

Colorado Area Codes by City

Find the right area code for your destination in the Centennial State.

CityRegionCode
DenverCentral / Metro303 / 720
Colorado SpringsSoutheast / Pikes Peak719
AuroraDenver Metro303 / 720
Fort CollinsNorthern Colorado970
BoulderFront Range303 / 720
CityRegionCode
Aspen / VailMountain Towns970
PuebloSouthern Colorado719
Grand JunctionWestern Slope970
DurangoSouthwest970
GreeleyNorthern Plains970

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Call Colorado?

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Frequently Asked Questions

What is the difference between 303 and 720?

303 is the original area code for Denver and the surrounding metro area. 720 was added later as an 'overlay' code. Both cover the exact same geographic area, and calls between them are considered local, but require 10-digit dialing.

How do I call a 970 number?

Dial +1 followed by 970 and the 7-digit number. This area code covers Northern Colorado (Fort Collins), Western Colorado (Grand Junction), and the mountain resort towns (Aspen, Vail).

What time is it in Colorado?

Colorado is in the Mountain Time Zone (MST/MDT). It is generally 2 hours behind New York (EST) and 1 hour ahead of California (PST).

Can I call Colorado mobiles for free?

StartACall offers very cheap rates to US mobiles, often at competitive rates. While not completely free, it is significantly cheaper than traditional international calling plans.

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Colorado area codes explained for international callers

In short

Colorado divides neatly into three calling regions: the Denver metro with its stack of overlay codes, the southern corridor around Colorado Springs and Pueblo on 719, and the mountain and northern communities on 970. Here is how the codes map to places, plus dialing steps and Mountain Time advice for callers overseas.

How the codes carve up the state

The Denver metropolitan area, including Boulder, Aurora and Lakewood, is served by 303 and its overlays 720 and 983. All three cover the same footprint, so a 720 mobile and a 303 landline can belong to next-door neighbors. The 983 code was added in 2022 as the region kept growing.

South of the metro, 719 covers Colorado Springs, Pueblo and the southeastern plains. Everything else, from Fort Collins and Greeley in the north to Grand Junction, Aspen and Durango in the mountains and west, sits under 970. Ski towns you may be calling, such as Vail and Breckenridge, are 970 numbers.

A few mountain communities near the Utah and Wyoming borders share exchanges with neighboring states, but as a rule the three regions hold firm. Colorado has avoided further splits by using overlays, which is why Denver numbers must always be dialed with all ten digits while some rural 970 towns still manage with seven locally.

Mountain Time and calling windows from abroad

The entire state observes Mountain Time, seven hours behind UTC in winter and six in summer. London is seven hours ahead of Denver for most of the year, so a 4pm call from the UK reaches Colorado at 9am. From Sydney, Colorado's business morning falls in the early hours, making the Australian morning to Colorado afternoon overlap easier.

Ski resorts and mountain businesses run long seasonal hours in winter, often answering from 8am, while summer hours can be shorter. Denver offices follow standard 9am to 5pm patterns. For personal calls, 6pm to 9pm Mountain Time is the dependable evening slot, which is early morning in much of Asia.

Remember that Colorado observes daylight saving, so the gap to countries that stay fixed, such as India, China and Japan, shifts by an hour every March and November. From Tokyo, Denver's business morning falls around midnight, so most Japan to Colorado calls happen in the Japanese morning instead, reaching Colorado in its late afternoon.

Dialing Colorado and what it costs

From outside North America, enter +1, then the area code, then the seven-digit number, for example +1 719 555 0173 for a Colorado Springs line. Local callers inside the overlay regions already dial ten digits, so the number you see printed is the number you dial after the +1.

Colorado mobiles use the same geographic codes as fixed lines and cost the same to reach. StartACall bills per minute on a pay-as-you-go basis with no subscription and no connection fee, and calls are placed directly from a browser, which suits travelers checking in with Denver from abroad.

If Colorado contacts need to call you back cheaply, a US virtual number, available from $2.14 to $5 per month, gives them a local-rate way to reach you wherever you are. It rings your browser wherever you happen to be, with no forwarding setup required.

Frequently asked questions

What area code is Denver Colorado?+

Denver uses 303, 720 and 983. All three are overlays covering the same metro territory including Boulder and Aurora, so any of them can appear on a Denver number. Older established businesses tend to hold 303 numbers, while newer mobiles often carry 720 or 983.

What area code is Colorado Springs?+

Colorado Springs is in the 719 area code, which also covers Pueblo and southeastern Colorado. From abroad, dial +1 719 and the seven-digit local number. Colorado Springs numbers never begin with 303 or 970, so the code is a reliable location check.

Which Colorado cities use area code 970?+

Area code 970 covers northern and western Colorado, including Fort Collins, Greeley, Grand Junction, Durango and the mountain resort towns such as Vail, Aspen and Breckenridge. If you are calling a ski resort, expect a 970 number to answer.

What time should I call Colorado from the UK?+

Colorado is on Mountain Time, seven hours behind London in winter. Call between 4pm and 11pm UK time to reach people during Colorado's business day and early evening. The difference shifts briefly each March and November, so recheck around those dates.

Is a 720 number a mobile number?+

Not necessarily. In the US, mobiles and landlines share the same geographic area codes, so 720 can be either. Calling either type costs the same per minute with StartACall. Only the owner can tell you whether it rings a handset or a desk phone.

Last reviewed June 2026Reviewed by the StartACall calling teamDialing rules cross checked against ITU international dialing procedures
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