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$71+ Cheap flights from San Francisco (SFO) 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 12/3. Fares are subject to change and may not be available on all flights or dates of travel.
SFO — DEN
Nov 28 — Dec 51
Fri 11/28
Fri 12/5
1 adult, Economy
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Cheapflights Tip: The best prices from San Francisco to Boulder are usually found in January or March, booked 53 days in advance, depart on a Friday or Saturday and return on a Thursday

Cheap flight deals from San Francisco to Boulder

Keep the following information in mind while searching for San Francisco to Boulder flight deals. Data was last updated October 29, 2025.

Most accurate provider

CheapOair
3 stars

Most trusted provider

CheapOair
3 stars

Round-trip from

$112
(Cheapflightsfares)

One-way from

$71
(Booking.com)

Popular in

June

Cheapest in

January

Average price

$236
Provider with most accurate pricing for San Francisco-Denver Intl flight deals.
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Provider most trusted by Cheapflights users for San Francisco-Denver Intl flights.
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From San Francisco to Boulder
Search Deals
One-way flight from San Francisco to Boulder
Search Deals
Highest demand for flights based on searches. 9% potential increase in price ($23 potential increase over avg. RT price).
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Cheapest flight prices on average. 1% potential price decrease ($5 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 Francisco to Boulder

Cheapest flights from San Francisco to Boulder
Explore the most affordable flight options available from San Francisco to Boulder. Find the lowest fares from popular airlines and budget airlines, with prices last updated on October 29, 2025.

This Cheapflightsfares deal was found by Cheapflights users on 10/27. 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.
Sat 12/66:30 amSFO - DEN
Nonstop2h 42mFrontier
Sun 12/76:00 amDEN - SFO
Nonstop2h 53mFrontier
Deal found 10/27$112
This Kiwi.com deal was found by Cheapflights users on 10/26. 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 12/910:10 pmSFO - DEN
1 stop11h 02mFrontier
Sun 12/146:00 amDEN - SFO
Nonstop2h 53mFrontier
Deal found 10/26$114
This Cheapflightsfares deal was found by Cheapflights users on 10/26. 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.
Thu 12/44:07 pmSFO - DEN
Nonstop2h 41mFrontier
Thu 12/1112:59 amDEN - SFO
1 stop13h 19mFrontier
Deal found 10/26$115
This Frontier deal was found by Cheapflights users on 10/26. 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 11/176:34 amSFO - DEN
Nonstop2h 44mFrontier
Wed 12/36:30 amDEN - SFO
1 stop11h 21mFrontier
Deal found 10/26$116
This Kiwi.com deal was found by Cheapflights users on 10/28. 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 11/128:02 amSFO - DEN
Nonstop2h 43mFrontier
Sat 11/1512:25 pmDEN - SFO
1 stop9h 46mFrontier
Deal found 10/28$117
This Frontier deal was found by Cheapflights users on 10/26. 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 11/202:54 pmSFO - DEN
Nonstop2h 40mFrontier
Thu 12/46:00 amDEN - SFO
Nonstop2h 53mFrontier
Deal found 10/26$118
This Frontier deal was found by Cheapflights users on 10/28. 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.
Fri 11/1410:23 pmSFO - DEN
1 stop9h 40mFrontier
Tue 11/188:39 pmDEN - SFO
Nonstop2h 48mFrontier
Deal found 10/28$119
This Frontier deal was found by Cheapflights users on 10/28. 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.
Sat 11/156:34 amSFO - DEN
Nonstop2h 44mFrontier
Tue 11/188:39 pmDEN - SFO
Nonstop2h 48mFrontier
Deal found 10/28$120
This Frontier deal was found by Cheapflights users on 10/28. 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.
Wed 11/128:02 amSFO - DEN
Nonstop2h 43mFrontier
Sun 11/167:45 amDEN - SFO
Nonstop2h 48mFrontier
Deal found 10/28$121
This Cheapflightsfares deal was found by Cheapflights users on 10/28. 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.
Tue 12/26:18 amSFO - DEN
Nonstop2h 42mFrontier
Sat 12/69:05 pmDEN - SFO
1 stop13h 49mFrontier
Deal found 10/28$124
This Frontier deal was found by Cheapflights users on 10/28. 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 11/1312:43 pmSFO - DEN
Nonstop2h 48mFrontier
Wed 11/192:15 pmDEN - SFO
1 stop8h 07mFrontier
Deal found 10/28$125

Cheapflights Fare Finder

 
Customize your flight search to find flights from San Francisco 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 29, 2025.
Use the filters below to find and compare flights from San Francisco to Boulder that are best for you.

Fly from

San Francisco

Fly to

Boulder

Route

Depart

Return

Price

San FranciscoDenver

SFO - DEN

SFODEN

San Francisco

Thu 1/15

5:50 am-9:20 am

Nonstop2h 30m

Denver Intl

Mon 1/19

6:10 am-10:30 am

1 stop5h 20m

$147

San FranciscoDenver

SFO - DEN

SFODEN

San Francisco

Tue 1/27

2:52 pm-11:58 pm

1 stop8h 06m

Denver Intl

Fri 1/30

7:00 am-2:02 pm

1 stop8h 02m

$156

San FranciscoDenver

SFO - DEN

SFODEN

San Francisco

Sat 12/6

8:55 pm-12:30 am

Nonstop2h 35m

Denver Intl

Sat 12/13

6:00 am-7:50 am

Nonstop2h 50m

$157

San FranciscoDenver

SFO - DEN

SFODEN

San Francisco

Thu 12/18

3:45 pm-11:25 pm

1 stop6h 40m

Denver Intl

Mon 12/22

6:10 pm-12:25 am

1 stop7h 15m

$177

San FranciscoDenver

SFO - DEN

SFODEN

San Francisco

Tue 1/27

10:30 am-11:58 pm

2 stops12h 28m

Denver Intl

Wed 1/28

8:04 am-2:02 pm

1 stop6h 58m

$185

San FranciscoDenver

SFO - DEN

SFODEN

San Francisco

Tue 1/27

6:25 am-10:05 am

Nonstop2h 40m

Denver Intl

Thu 1/29

5:18 am-7:14 am

Nonstop2h 56m

$187

San FranciscoDenver

SFO - DEN

SFODEN

San Francisco

Wed 12/3

7:45 am-3:55 pm

2 stops7h 10m

Denver Intl

Wed 12/10

1:25 pm-8:10 pm

2 stops7h 45m

$187

San FranciscoDenver

SFO - DEN

SFODEN

San Francisco

Thu 12/4

7:40 am-3:55 pm

2 stops7h 15m

Denver Intl

Mon 12/8

1:25 pm-8:10 pm

2 stops7h 45m

$187

San FranciscoDenver

SFO - DEN

SFODEN

San Francisco

Wed 12/3

6:00 am-11:09 am

1 stop4h 09m

Denver Intl

Wed 12/3

6:22 pm-10:13 pm

1 stop4h 51m

$197

San FranciscoDenver

SFO - DEN

SFODEN

San Francisco

Wed 12/17

7:35 am-9:28 pm

2 stops12h 53m

Denver Intl

Mon 12/22

6:48 pm-12:27 am

1 stop6h 39m

$201

Flights are sorted by cheapest round-trip flights first.

Deals found on 10/28

Showing 1-10 of 23 results
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2
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Best time to book a flight from San Francisco to Boulder

Have a flexible travel schedule? Discover the best time to fly to Boulder from San Francisco 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 Francisco to Boulder

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

Use this chart to determine the optimal time to book a round-trip flight from San Francisco to Boulder. Price data was last updated on October 24, 2025.

Booking 53 days in advance of your planned departure date is, on average, the best time to get cheap flights from San Francisco 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 Francisco to Boulder?

Currently, February is the cheapest month in which you can book a flight from San Francisco to Boulder (average of $28). Flying from San Francisco to Boulder in June is currently the most expensive (average of $106). 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 SFO to BD9?

Find hourly flight availability from San Francisco 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 29, 2025.

It’s typically best to fly out from San Francisco to Boulder in the morning. Doing so could potentially save you 8% on the flight price compared to flying at noon, which is usually more expensive.

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

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

Travelers seeking maximum savings on their San Francisco to Boulder flight should consider departing on Friday mornings 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.

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 29, 2025.
Peruse reviews from past customers who have flown with Southwest, United Airlines, and American Airlines from San Francisco to Boulder to help guide your decision. You can also see how each airline stacks up in terms of entertainment options, comfort, food, crew/service, and boarding process.
Southwest
8.0
Very good
4,240 reviews

Overall

8.0

Comfort

8.0

Entertainment

7.5

Food

7.0

Boarding

8.1

Crew

8.6

Reviews

1 / 20
8.0
Excellent

Walter,Aug 2025

OAK - SAN

Dozens of flights and I've never seen a row's beverages forgotten. I even went back and asked the attendant to check on them and nothing. I really hope it didn't have something to do with the Black mother with her kid in the row. Otherwise it was a typical Southwest flight, rapid boarding, tolerable leg room.
Southwest
8.0
Very good
4,240 reviews
Southwest
8.0
Very good
4,240 reviews

Overall

8.0

Comfort

8.0

Entertainment

7.5

Food

7.0

Boarding

8.1

Crew

8.6

Reviews

1 / 20
8.0
Excellent

Walter,Aug 2025

OAK - SAN

Dozens of flights and I've never seen a row's beverages forgotten. I even went back and asked the attendant to check on them and nothing. I really hope it didn't have something to do with the Black mother with her kid in the row. Otherwise it was a typical Southwest flight, rapid boarding, tolerable leg room.
United Airlines
7.4
Good
9,001 reviews
Southwest
8.0
Very good
4,240 reviews

Overall

8.0

Comfort

8.0

Entertainment

7.5

Food

7.0

Boarding

8.1

Crew

8.6

Reviews

1 / 20
8.0
Excellent

Walter,Aug 2025

OAK - SAN

Dozens of flights and I've never seen a row's beverages forgotten. I even went back and asked the attendant to check on them and nothing. I really hope it didn't have something to do with the Black mother with her kid in the row. Otherwise it was a typical Southwest flight, rapid boarding, tolerable leg room.
American Airlines
7.2
Good
11,032 reviews
Southwest
8.0
Very good
4,240 reviews

Overall

8.0

Comfort

8.0

Entertainment

7.5

Food

7.0

Boarding

8.1

Crew

8.6

Reviews

1 / 20
8.0
Excellent

Walter,Aug 2025

OAK - SAN

Dozens of flights and I've never seen a row's beverages forgotten. I even went back and asked the attendant to check on them and nothing. I really hope it didn't have something to do with the Black mother with her kid in the row. Otherwise it was a typical Southwest flight, rapid boarding, tolerable leg room.
Allegiant Air
7.2
Good
695 reviews
Southwest
8.0
Very good
4,240 reviews

Overall

8.0

Comfort

8.0

Entertainment

7.5

Food

7.0

Boarding

8.1

Crew

8.6

Reviews

1 / 20
8.0
Excellent

Walter,Aug 2025

OAK - SAN

Dozens of flights and I've never seen a row's beverages forgotten. I even went back and asked the attendant to check on them and nothing. I really hope it didn't have something to do with the Black mother with her kid in the row. Otherwise it was a typical Southwest flight, rapid boarding, tolerable leg room.
Frontier
5.8
Fair
3,124 reviews
Southwest
8.0
Very good
4,240 reviews

Overall

8.0

Comfort

8.0

Entertainment

7.5

Food

7.0

Boarding

8.1

Crew

8.6

Reviews

1 / 20
8.0
Excellent

Walter,Aug 2025

OAK - SAN

Dozens of flights and I've never seen a row's beverages forgotten. I even went back and asked the attendant to check on them and nothing. I really hope it didn't have something to do with the Black mother with her kid in the row. Otherwise it was a typical Southwest flight, rapid boarding, tolerable leg room.

Related info for your journey

Find useful and relevant information for your journey from San Francisco 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 Francisco to Boulder?

    Located just 11.8 mi from the city center, San Francisco is the airport most travelers will use when flying to Boulder from San Francisco. Booking flights from San Francisco (SFO) to Boulder should be relatively easy as there are 34 daily outbound flights to Boulder from 6 different airlines.

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

    This flight path from San Francisco to Boulder was viewed by 269 users in the past month. Keep an eye out for changes in search interest prior to high and low season.

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

    Airlines like Southwest, Alaska Airlines, and United Airlines fly from San Francisco to Boulder in about 2h 30m. The time it takes to get you to your destination can typically vary by up to 5h 36m. There are 964 mi between San Francisco and Boulder. When browsing for deals, the options you’ll see will be for both nonstop flights and flights with stops.

  • What are the cheapest airlines to fly from San Francisco to Boulder one-way?

    For one-way options, check prices for Alaska Airlines. According to our data, you can fly for as low as $74. Users have also found prices from $79 and $79 on Southwest and United Airlines, respectively.

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

    Consider SWISS (93%), Asiana Airlines (88%) or Virgin Australia (85%) when booking your flight. These represent the most reliable airlines when flying from San Francisco to Boulder.

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

    The cheapest flight price from San Francisco to Boulder is $76. On average you can expect to pay $890. The most popular route, (San Francisco - Denver Intl), can usually be booked for $53.

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

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

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

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

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

    Yes. Cheapflights offers flight deals from San Francisco 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 Francisco to Boulder?

    Currently, February is the cheapest month in which you can book a flight from San Francisco to Boulder (average of $28). Flying from San Francisco to Boulder in June is currently the most expensive (average of $106). 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 6 airlines flying from San Francisco to Boulder

Discover the top 6 airlines that operate flights from San Francisco 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 29, 2025.
AirlineCheapestAverageFlexibilityOn-time
FrontierCheapest$69Average$183FlexibilityNo cancel feeOn-time62%
Allegiant AirCheapest$88Average$100FlexibilityNo cancel feeOn-time88%
SouthwestCheapest$157Average$334FlexibilityNo cancel feeOn-time63%
United AirlinesCheapest$171Average$385FlexibilityNo cancel feeOn-time69%
DeltaCheapest$175Average$290FlexibilityNo cancel feeOn-timeN/A
American AirlinesCheapest$176Average$428FlexibilityNo cancel feeOn-time71%

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