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$79+ 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 9/23. Fares are subject to change and may not be available on all flights or dates of travel.
SFO — DEN
ago. 3 — ago. 101
dom. 8/3
dom. 8/10
1 adult, Economy
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Cheapflights Tip: The best prices from San Francisco to Boulder are usually found in January or October, booked 52 days in advance, depart on a Saturday or Friday and return on a Friday

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 julio 29, 2025.

Round-trip from

$149
(Frontier)

One-way from

$79
(Southwest)

Popular in

June

Cheapest in

January

Average price

$257
From San Francisco to Boulder
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One-way flight from San Francisco to Boulder
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Highest demand for flights based on searches. 12% potential increase in price ($30 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 July 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 julio 29, 2025.

This Frontier deal was found by Cheapflights users on 7/29. 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.
mié. 8/136:37 amSFO - DEN
Nonstop2h 40mFrontier
sáb. 8/169:36 pmDEN - SFO
Nonstop2h 49mFrontier
Deal found 7/29$149
This Kiwi.com deal was found by Cheapflights users on 7/28. 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.
dom. 10/128:04 pmSFO - DEN
Nonstop2h 41mMultiple Airlines
mar. 10/217:01 amDEN - SFO
1 stop8h 00mMultiple Airlines
Deal found 7/28$154
This Southwest deal was found by Cheapflights users on 7/28. 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 Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
mié. 10/228:30 amSFO - DEN
Nonstop2h 30mSouthwest
sáb. 10/252:10 pmDEN - SFO
Nonstop2h 35mSouthwest
Deal found 7/28$157
This Alaska Airlines deal was found by Cheapflights users on 7/28. 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 Alaska Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
mié. 9/1711:30 amSFO - DEN
1 stop7h 57mAlaska Airlines
mar. 9/2311:40 amDEN - SFO
1 stop5h 44mAlaska Airlines
Deal found 7/28$176
This American Airlines deal was found by Cheapflights users on 7/28. 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 American Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
mié. 8/2711:21 amSFO - DEN
1 stop5h 08mAmerican Airlines
mié. 9/38:00 amDEN - SFO
1 stop6h 08mAmerican Airlines
Deal found 7/28$187

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 julio 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

mié. 8/13

6:37 am-10:17 am

Nonstop2h 40m

Denver Intl

sáb. 8/16

9:36 pm-11:25 pm

Nonstop2h 49m

$149

San FranciscoDenver

SFO - DEN

SFODEN

San Francisco

dom. 10/12

8:04 pm-11:45 pm

Nonstop2h 41m

Denver Intl

mar. 10/21

7:01 am-2:01 pm

1 stop8h 00m

$154

San FranciscoDenver

SFO - DEN

SFODEN

San Francisco

mié. 10/22

8:30 am-12:00 pm

Nonstop2h 30m

Denver Intl

sáb. 10/25

2:10 pm-3:45 pm

Nonstop2h 35m

$157

San FranciscoDenver

SFO - DEN

SFODEN

San Francisco

mié. 9/17

11:30 am-8:27 pm

1 stop7h 57m

Denver Intl

mar. 9/23

11:40 am-4:24 pm

1 stop5h 44m

$176

San FranciscoDenver

SFO - DEN

SFODEN

San Francisco

mié. 8/27

11:21 am-5:29 pm

1 stop5h 08m

Denver Intl

mié. 9/3

8:00 am-1:08 pm

1 stop6h 08m

$187

San FranciscoDenver

SFO - DEN

SFODEN

San Francisco

jue. 10/23

10:12 am-7:10 pm

1 stop7h 58m

Denver Intl

sáb. 10/25

7:01 am-2:01 pm

1 stop8h 00m

$196

San FranciscoDenver

SFO - DEN

SFODEN

San Francisco

mar. 9/23

8:35 am-12:00 pm

Nonstop2h 25m

$79

San FranciscoDenver

SFO - DEN

SFODEN

San Francisco

vie. 8/22

9:21 am-1:00 pm

Nonstop2h 39m

$82

San FranciscoDenver

SFO - DEN

SFODEN

San Francisco

mié. 9/24

11:30 am-8:27 pm

1 stop7h 57m

$88

San FranciscoDenver

SFO - DEN

SFODEN

San Francisco

mar. 9/2

4:25 pm-11:10 pm

1 stop5h 45m

$94

Flights are sorted by cheapest round-trip flights first.

Deals found on 7/28

Showing 1-10 of 13 results
1
2

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 July 25, 2025.

Booking 52 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, October is the cheapest month in which you can book a flight from San Francisco to Boulder (average of $197). Flying from San Francisco to Boulder in March is currently the most expensive (average of $278). 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 julio 29, 2025.

Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from San Francisco to Boulder as you normally would.

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 October 6, 2024.

Travelers seeking maximum savings on their San Francisco to Boulder flight should consider departing on Thursday evenings 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 Francisco to Boulder

Explore weekly flight availability from San Francisco 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 julio 29, 2025.

The most flights from SFO to BD9 are scheduled on a Monday (56 on average). You will have fewer flight options on Wednesday, which is when the least amount of flights are scheduled (32 on average).

How much does it cost to fly round-trip from San Francisco to Boulder?

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 julio 29, 2025.
Peruse reviews from past customers who have flown with Alaska Airlines, Southwest, and Delta 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.
Alaska Airlines
8.0
Very good
10,000 reviews

Food

7.1

Overall

8.0

Boarding

8.1

Entertainment

7.1

Crew

8.5

Comfort

7.8

Reviews

1 / 20
10.0
Excellent

James,Apr 2025

LAX - SFO

Good flight except the uncontrollable cold air from the ceiling.
Alaska Airlines
8.0
Very good
10,000 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Food

7.1

Overall

8.0

Boarding

8.1

Entertainment

7.1

Crew

8.5

Comfort

7.8

Reviews

1 / 20
10.0
Excellent

James,Apr 2025

LAX - SFO

Good flight except the uncontrollable cold air from the ceiling.
Southwest
8.0
Very good
4,238 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Food

7.1

Overall

8.0

Boarding

8.1

Entertainment

7.1

Crew

8.5

Comfort

7.8

Reviews

1 / 20
10.0
Excellent

James,Apr 2025

LAX - SFO

Good flight except the uncontrollable cold air from the ceiling.
Delta
8.0
Very good
7,979 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Food

7.1

Overall

8.0

Boarding

8.1

Entertainment

7.1

Crew

8.5

Comfort

7.8

Reviews

1 / 20
10.0
Excellent

James,Apr 2025

LAX - SFO

Good flight except the uncontrollable cold air from the ceiling.
Hawaiian Airlines
7.8
Good
2,605 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Food

7.1

Overall

8.0

Boarding

8.1

Entertainment

7.1

Crew

8.5

Comfort

7.8

Reviews

1 / 20
10.0
Excellent

James,Apr 2025

LAX - SFO

Good flight except the uncontrollable cold air from the ceiling.
United Airlines
7.4
Good
8,896 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Food

7.1

Overall

8.0

Boarding

8.1

Entertainment

7.1

Crew

8.5

Comfort

7.8

Reviews

1 / 20
10.0
Excellent

James,Apr 2025

LAX - SFO

Good flight except the uncontrollable cold air from the ceiling.

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 47 daily outbound flights to Boulder from 7 different airlines.

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

    This flight path from San Francisco to Boulder was viewed by 270 users in the past month. Keep an eye out for changes in search interest prior to high and low season.

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

    For one-way options, check prices for Southwest. According to our data, you can fly for as low as $79. Users have also found prices from $82 and $88 on Frontier and Alaska Airlines, respectively.

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

    Consider Asiana Airlines (78%), Air Canada (76%) or United Airlines (75%) 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 $92. On average you can expect to pay $759. The most popular route, (San Francisco - Denver Intl), can usually be booked for $97.

  • 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, October is the cheapest month in which you can book a flight from San Francisco to Boulder (average of $197). Flying from San Francisco to Boulder in March is currently the most expensive (average of $278). 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 Francisco to Boulder

Discover the top 7 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 julio 29, 2025.
AirlineCheapestAverageFlexibilityOn-time
FrontierCheapest$63Average$171FlexibilityNo cancel feeOn-time62%
Allegiant AirCheapest$88Average$100FlexibilityNo cancel feeOn-time88%
Alaska AirlinesCheapest$116Average$320FlexibilityNo cancel feeOn-time75%
SouthwestCheapest$157Average$324FlexibilityNo cancel feeOn-time63%
United AirlinesCheapest$159Average$397FlexibilityNo cancel feeOn-time69%
DeltaCheapest$175Average$280FlexibilityNo cancel feeOn-timeN/A
American AirlinesCheapest$176Average$319FlexibilityNo cancel feeOn-time71%

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