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$41+ Cheap flights from San Diego (SAN) to Boulder, CO

This is the cheapest one-way flight price found by a Cheapflights user in the last 72 hours by searching for a flight departing on 1/17. Fares are subject to change and may not be available on all flights or dates of travel.
SAN — DEN
Nov 15 — Nov 221
Sat 11/15
Sat 11/22
1 adult, Economy
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Cheapflights Tip: The best prices from San Diego to Boulder are usually found in January or October, booked 58 days in advance, depart on a Friday or Saturday and return on a Tuesday

Cheap flight deals from San Diego to Boulder

Keep the following information in mind while searching for San Diego to Boulder flight deals. Data was last updated October 16, 2025.

Most accurate provider

FlightHub
3 stars

Most trusted provider

FlightHub
3 stars

Round-trip from

$79
(Kiwi.com)

One-way from

$41
(Cheapflightsfares)

Popular in

March

Cheapest in

January

Average price

$149
Provider with most accurate pricing for San Diego-Denver Intl flight deals.
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Provider most trusted by Cheapflights users for San Diego-Denver Intl flights.
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From San Diego to Boulder
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One-way flight from San Diego to Boulder
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Highest demand for flights based on searches. 6% potential increase in price ($12 potential increase over avg. RT price).
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Cheapest flight prices on average. 3% potential price decrease ($7 potential savings vs. average RT price).
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Average for round-trip flights in October 2025
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Find flight deals from San Diego to Boulder

Cheapest flights from San Diego to Boulder
Explore the most affordable flight options available from San Diego to Boulder. Find the lowest fares from popular airlines and budget airlines, with prices last updated on October 16, 2025.

This Kiwi.com deal was found by Cheapflights users on 10/16. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 11/256:36 amSAN - DEN
Nonstop2h 38mFrontier
Fri 11/2810:29 pmDEN - SAN
Nonstop2h 30mFrontier
Deal found 10/16$79
This Kiwi.com deal was found by Cheapflights users on 10/15. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 11/15:28 pmSAN - DEN
Nonstop2h 31mFrontier
Mon 11/310:29 pmDEN - SAN
Nonstop2h 21mFrontier
Deal found 10/15$82
This Frontier deal was found by Cheapflights users on 10/14. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 10/306:00 pmSAN - DEN
Nonstop2h 34mFrontier
Sat 11/18:00 amDEN - SAN
Nonstop2h 27mFrontier
Deal found 10/14$83
This Cheapflightsfares deal was found by Cheapflights users on 10/15. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Cheapflightsfares is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 10/276:41 amSAN - DEN
Nonstop2h 37mFrontier
Tue 10/2812:00 pmDEN - SAN
Nonstop2h 28mFrontier
Deal found 10/15$84
This Kiwi.com deal was found by Cheapflights users on 10/16. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 11/69:14 amSAN - DEN
1 stop4h 42mFrontier
Sun 11/910:29 pmDEN - SAN
Nonstop2h 21mFrontier
Deal found 10/16$85
This Kiwi.com deal was found by Cheapflights users on 10/15. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 11/128:00 amSAN - DEN
1 stop10h 12mFrontier
Wed 11/1910:20 amDEN - SAN
Nonstop2h 32mFrontier
Deal found 10/15$87
This Frontier deal was found by Cheapflights users on 10/16. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 12/226:25 amSAN - DEN
Nonstop2h 38mFrontier
Fri 12/2610:29 pmDEN - SAN
Nonstop2h 30mFrontier
Deal found 10/16$89
This Kiwi.com deal was found by Cheapflights users on 10/13. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 12/86:25 amSAN - DEN
Nonstop2h 38mFrontier
Wed 12/109:02 pmDEN - SAN
Nonstop2h 31mFrontier
Deal found 10/13$90
This Kiwi.com deal was found by Cheapflights users on 10/14. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 12/116:25 amSAN - DEN
Nonstop2h 38mFrontier
Wed 12/1711:55 amDEN - SAN
Nonstop2h 35mFrontier
Deal found 10/14$91
This Kiwi.com deal was found by Cheapflights users on 10/15. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 11/66:00 pmSAN - DEN
Nonstop2h 34mFrontier
Sat 11/83:05 pmDEN - SAN
1 stop6h 19mFrontier
Deal found 10/15$92

Cheapflights Fare Finder

 
Customize your flight search to find flights from San Diego to Boulder that fit within your specific budget. Explore options based on user searches and filter the results based on your desired price range. Find flights that match your budget for a cost-effective journey. Over the last 7 days, Cheapflights users made 2,558,603 searches. Data last updated October 16, 2025.
Use the filters below to find and compare flights from San Diego to Boulder that are best for you.

Fly from

San Diego

Fly to

Boulder

Route

Depart

Return

Price

San DiegoDenver

SAN - DEN

SANDEN

San Diego

Sat 11/15

3:48 pm-7:06 pm

Nonstop2h 18m

Denver Intl

Mon 11/24

6:00 am-7:34 am

Nonstop2h 34m

$117

San DiegoDenver

SAN - DEN

SANDEN

San Diego

Thu 11/13

6:47 pm-10:17 pm

Nonstop2h 30m

Denver Intl

Sun 2/15

3:50 pm-5:10 pm

Nonstop2h 20m

$117

San DiegoDenver

SAN - DEN

SANDEN

San Diego

Thu 11/20

3:48 pm-7:06 pm

Nonstop2h 18m

Denver Intl

Mon 11/24

6:00 am-7:34 am

Nonstop2h 34m

$117

San DiegoDenver

SAN - DEN

SANDEN

San Diego

Sat 11/22

8:33 pm-11:59 pm

Nonstop2h 26m

Denver Intl

Mon 11/24

7:20 pm-8:48 pm

Nonstop2h 28m

$117

San DiegoDenver

SAN - DEN

SANDEN

San Diego

Sat 11/8

3:48 pm-7:06 pm

Nonstop2h 18m

Denver Intl

Tue 11/11

12:49 pm-2:15 pm

Nonstop2h 26m

$117

San DiegoDenver

SAN - DEN

SANDEN

San Diego

Fri 12/26

6:35 am-10:05 am

Nonstop2h 30m

Denver Intl

Fri 1/2

3:30 pm-6:45 pm

1 stop4h 15m

$122

San DiegoDenver

SAN - DEN

SANDEN

San Diego

Fri 12/5

8:40 am-1:35 pm

1 stop3h 55m

Denver Intl

Sun 12/7

10:10 am-11:35 am

Nonstop2h 25m

$122

San DiegoDenver

SAN - DEN

SANDEN

San Diego

Fri 12/12

5:35 pm-10:35 pm

1 stop4h 00m

Denver Intl

Mon 12/15

8:40 am-10:10 am

Nonstop2h 30m

$122

San DiegoDenver

SAN - DEN

SANDEN

San Diego

Fri 11/14

5:55 pm-12:30 am

1 stop5h 35m

Denver Intl

Sun 2/15

3:50 pm-5:10 pm

Nonstop2h 20m

$123

San DiegoDenver

SAN - DEN

SANDEN

San Diego

Sat 11/22

6:35 pm-12:25 am

1 stop4h 50m

Denver Intl

Fri 11/28

5:40 am-7:15 am

Nonstop2h 35m

$127

Flights are sorted by cheapest round-trip flights first.

Deals found on 10/16

Showing 1-10 of 23 results
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Best time to book a flight from San Diego to Boulder

Have a flexible travel schedule? Discover the best time to fly to Boulder from San Diego with our price prediction graph.
Estimated round-trip price
Rates are based on past data. Find the cheapest month and day to book your flight based on your travel requirements, then search for cheap deals.

Cheapflights Insights

Everything you need to know about your flight from San Diego to Boulder

How far ahead should I book a flight from San Diego to Boulder?

Use this chart to determine the optimal time to book a round-trip flight from San Diego to Boulder. Price data was last updated on October 10, 2025.

Booking 58 days in advance of your planned departure date is, on average, the best time to get cheap flights from San Diego to Boulder. The general trend is that the closer you book to the departure date, the more expensive your flight will be.

What is the cheapest month to book a flight from San Diego to Boulder?

Currently, January is the cheapest month in which you can book a flight from San Diego to Boulder (average of $24). Flying from San Diego to Boulder in May is currently the most expensive (average of $66). There are several factors that can impact the price of a flight, so comparing airlines, departure airports and flight times can provide users with more options.

What is the cheapest time of day to fly from SAN to BD9?

Find hourly flight availability from San Diego to Boulder. Discover flight options and departure times throughout the day, allowing you to choose a departure time that suits your schedule. Data last updated October 16, 2025.

A simple way to save on the total cost of your ticket is to fly from San Diego to Boulder in the afternoon. If you’re flexible enough to do this you can expect to save up to 28% on your trip compared to booking a flight at noon.

What is the cheapest day to fly from San Diego to Boulder?

Use this chart to determine the cheapest time to fly round-trip from San Diego to Boulder. Price data was last updated on December 16, 2024.

Travelers seeking maximum savings on their San Diego to Boulder flight should consider departing on Saturday afternoons when fares are most often at their lowest. Sunday at noon flights should be avoided if possible as fares are typically the most expensive at this time.

Weekly flight availability from San Diego to Boulder

Explore weekly flight availability from San Diego to Boulder. Discover flights operating on different days of the week, giving you the flexibility to choose a travel day that best fits your plans. Compare info to find the most convenient option for your journey. Data last updated October 16, 2025.

The most flights from SAN to BD9 are scheduled on a Thursday (37 on average). You will have fewer flight options on Saturday, which is when the least amount of flights are scheduled (16 on average).

Reviews of airlines servicing Boulder

Get insights into the airlines that provide service to Boulder. Read reviews, discover amenities, and learn about the overall travel experience offered by airlines. Use this information to make informed decisions when choosing an airline for your flight to Boulder. Reviews last updated October 16, 2025.
See what other customers who have flown with Alaska Airlines, Southwest, and Hawaiian Airlines from San Diego to Boulder have to say. You can also see how each airline compares in terms of entertainment options, comfort, food, crew/service, and boarding process.
Alaska Airlines
8.0
Very good
11,102 reviews

Food

7.1

Boarding

8.1

Entertainment

7.0

Overall

8.0

Comfort

7.8

Crew

8.5

Reviews

1 / 20
6.0
Good

Hannah,Aug 2025

SFO - SAN

Ticket said TSA pre check, but then the TSA agent said that Alaska Airlines has not actually entered the pre check information for the ticket, so I had to use regular security. During boarding, I have a disability and need to board early. The Alaska Airlines employee announced disability boarding, but then immediately announced 2 other groups to board, so I still had to fight the crowds. On the plane, the stewardess was brusk and rude. Seats were very uncomfortable, especially on lower back.
Alaska Airlines
8.0
Very good
11,102 reviews
Alaska Airlines
8.0
Very good
11,102 reviews

Food

7.1

Boarding

8.1

Entertainment

7.0

Overall

8.0

Comfort

7.8

Crew

8.5

Reviews

1 / 20
6.0
Good

Hannah,Aug 2025

SFO - SAN

Ticket said TSA pre check, but then the TSA agent said that Alaska Airlines has not actually entered the pre check information for the ticket, so I had to use regular security. During boarding, I have a disability and need to board early. The Alaska Airlines employee announced disability boarding, but then immediately announced 2 other groups to board, so I still had to fight the crowds. On the plane, the stewardess was brusk and rude. Seats were very uncomfortable, especially on lower back.
Southwest
8.0
Very good
4,241 reviews
Alaska Airlines
8.0
Very good
11,102 reviews

Food

7.1

Boarding

8.1

Entertainment

7.0

Overall

8.0

Comfort

7.8

Crew

8.5

Reviews

1 / 20
6.0
Good

Hannah,Aug 2025

SFO - SAN

Ticket said TSA pre check, but then the TSA agent said that Alaska Airlines has not actually entered the pre check information for the ticket, so I had to use regular security. During boarding, I have a disability and need to board early. The Alaska Airlines employee announced disability boarding, but then immediately announced 2 other groups to board, so I still had to fight the crowds. On the plane, the stewardess was brusk and rude. Seats were very uncomfortable, especially on lower back.
Hawaiian Airlines
7.8
Good
2,781 reviews
Alaska Airlines
8.0
Very good
11,102 reviews

Food

7.1

Boarding

8.1

Entertainment

7.0

Overall

8.0

Comfort

7.8

Crew

8.5

Reviews

1 / 20
6.0
Good

Hannah,Aug 2025

SFO - SAN

Ticket said TSA pre check, but then the TSA agent said that Alaska Airlines has not actually entered the pre check information for the ticket, so I had to use regular security. During boarding, I have a disability and need to board early. The Alaska Airlines employee announced disability boarding, but then immediately announced 2 other groups to board, so I still had to fight the crowds. On the plane, the stewardess was brusk and rude. Seats were very uncomfortable, especially on lower back.
United Airlines
7.4
Good
8,982 reviews
Alaska Airlines
8.0
Very good
11,102 reviews

Food

7.1

Boarding

8.1

Entertainment

7.0

Overall

8.0

Comfort

7.8

Crew

8.5

Reviews

1 / 20
6.0
Good

Hannah,Aug 2025

SFO - SAN

Ticket said TSA pre check, but then the TSA agent said that Alaska Airlines has not actually entered the pre check information for the ticket, so I had to use regular security. During boarding, I have a disability and need to board early. The Alaska Airlines employee announced disability boarding, but then immediately announced 2 other groups to board, so I still had to fight the crowds. On the plane, the stewardess was brusk and rude. Seats were very uncomfortable, especially on lower back.
Frontier
5.8
Fair
3,137 reviews
Alaska Airlines
8.0
Very good
11,102 reviews

Food

7.1

Boarding

8.1

Entertainment

7.0

Overall

8.0

Comfort

7.8

Crew

8.5

Reviews

1 / 20
6.0
Good

Hannah,Aug 2025

SFO - SAN

Ticket said TSA pre check, but then the TSA agent said that Alaska Airlines has not actually entered the pre check information for the ticket, so I had to use regular security. During boarding, I have a disability and need to board early. The Alaska Airlines employee announced disability boarding, but then immediately announced 2 other groups to board, so I still had to fight the crowds. On the plane, the stewardess was brusk and rude. Seats were very uncomfortable, especially on lower back.

Related info for your journey

Find useful and relevant information for your journey from San Diego to Boulder. Access travel guides, tips, and recommendations to enhance your travel experience. Get information about local attractions, weather, transportation options, and more.

  • What airport do you fly from for flights from San Diego to Boulder?

    San Diego (SAN), located 2.6 mi from the city center, is the airport you fly out of when you book flights from San Diego to Boulder. 7 airlines have flights from San Diego to Boulder on a regular basis. Booking flights from San Diego to Boulder should not be difficult; the airport handles an average of 27 outbound flights to Boulder per day.

  • How popular is this San Diego to Boulder flight route?

    Flights from San Diego to Boulder have been viewed 188 times in the past calendar month.

  • How long is the flight from San Diego to Boulder?

    There are many flights that can get you from San Diego to Boulder in 2h 18m. Fly via Alaska Airlines or United Airlines to get the fastest option. There are 852 mi between San Diego and Boulder. Most flights are nonstop.

  • What are the most reliable airlines from San Diego to Boulder?

    No one likes to see their flight delayed. When booking a flight from San Diego to Boulder consider choosing SWISS (93%), Alaska Airlines (91%) or Hawaiian Airlines (91%) as they are the most reliable in getting you off to your destination on time.

  • What are the cheapest flights from San Diego to Boulder?

    On average you can expect to pay $750 for a flight from San Diego to Boulder. The cheapest flight overall is $58 while the most popular route, (San Diego - Denver Intl) is currently priced at $53.

  • Can I find deals for flights from San Diego to Boulder that include hotel bookings?

    Yes. In addition to deals on San Diego to Boulder flights, Cheapflights offers vacation packages that include both flights and hotel.

  • How can I find direct flights from San Diego to Boulder?

    After entering your origin and destination, apply the non-stop filter on the search result page to find direct flights from San Diego to Boulder.

  • Can I find deals for business class flights from San Diego to Boulder?

    Yes. Cheapflights offers flight deals from San Diego to Boulder by cabin class. In addition to browsing deals, you can also filter by cabin class on the search results page after making a search.

  • What is the cheapest month to book a flight from San Diego to Boulder?

    Currently, January is the cheapest month in which you can book a flight from San Diego to Boulder (average of $24). Flying from San Diego to Boulder in May is currently the most expensive (average of $66). There are several factors that can impact the price of a flight, so comparing airlines, departure airports and flight times can provide users with more options.

See more FAQs

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Top 7 airlines flying from San Diego to Boulder

Discover the top 7 airlines that operate flights from San Diego to Boulder. Compare their services, reliability, and customer satisfaction ratings to choose the airline that best suits your travel preferences and needs. Over the last 7 days, Cheapflights users made 2,558,603 searches. Data last updated October 16, 2025.
AirlineCheapestAverageFlexibilityOn-time
Hawaiian AirlinesCheapest$68Average$192FlexibilityNo cancel feeOn-time85%
FrontierCheapest$68Average$160FlexibilityNo cancel feeOn-time62%
Alaska AirlinesCheapest$103Average$194FlexibilityNo cancel feeOn-time75%
SouthwestCheapest$135Average$325FlexibilityNo cancel feeOn-time63%
United AirlinesCheapest$154Average$347FlexibilityNo cancel feeOn-time69%
DeltaCheapest$206Average$297FlexibilityNo cancel feeOn-timeN/A
American AirlinesCheapest$218Average$380FlexibilityNo cancel feeOn-time71%

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