HomeSearch by dateVacation packagesHotelsFlight dealsCar rentalTravel tips & news
Boulder

$62+ 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 2/9. Fares are subject to change and may not be available on all flights or dates of travel.
SFO — DEN
Jan 14 — Jan 211
Wed 1/14
Wed 1/21
1 adult, Economy
We work with more than 300 partners to bring you better travel deals

Find cheap flights from San Francisco to Boulder with Cheapflights

1. Tell us where you want to go

Enter your travel information like dates, passengers, trip type (one-way or round trip), and preferred cabin class then click “Find deals”

2. Select your favorite providers

We find the providers serving your travel needs. Choose up to four travel providers to compare side-by-side for flights, hotels, or car rentals.

3. Compare prices and book

Review each provider’s pricing and select the best option for you! Book through your favorite provider’s website for a seamless experience.

Cheapflights Tip: The best prices from San Francisco to Boulder are usually found in January or February, booked 53 days in advance, depart on a Friday or Tuesday and return on a Friday

Cheap 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 December 15, 2025.

This Frontier deal was found by Cheapflights users on 12/14. 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.
Tue 12/308:12 pmSFO - DEN
1 stop11h 43mFrontier
Fri 1/96:10 amDEN - SFO
Nonstop2h 53mFrontier
Deal found 12/14$146
This Kiwi.com deal was found by Cheapflights users on 12/15. 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.
Tue 12/308:12 pmSFO - DEN
1 stop11h 43mFrontier
Wed 1/710:29 pmDEN - SFO
1 stop12h 17mFrontier
Deal found 12/15$157
This Frontier deal was found by Cheapflights users on 12/14. 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.
Wed 12/311:29 pmSFO - DEN
1 stop8h 10mFrontier
Mon 1/57:00 amDEN - SFO
1 stop6h 34mFrontier
Deal found 12/14$163
This Frontier deal was found by Cheapflights users on 12/14. 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.
Wed 12/316:24 amSFO - DEN
Nonstop2h 42mFrontier
Fri 1/96:10 amDEN - SFO
Nonstop2h 53mFrontier
Deal found 12/14$178
This Frontier deal was found by Cheapflights users on 12/14. 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.
Wed 12/316:24 amSFO - DEN
Nonstop2h 42mFrontier
Sat 1/106:48 pmDEN - SFO
Nonstop2h 59mFrontier
Deal found 12/14$189
This Kiwi.com deal was found by Cheapflights users on 12/14. 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.
Wed 12/249:30 pmSFO - DEN
1 stop11h 36mFrontier
Tue 1/611:04 amDEN - SFO
1 stop12h 55mFrontier
Deal found 12/14$192
This Kiwi.com deal was found by Cheapflights users on 12/14. 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.
Tue 12/308:12 pmSFO - DEN
1 stop11h 43mMultiple Airlines
Tue 1/63:46 pmDEN - SFO
1 stop9h 08mMultiple Airlines
Deal found 12/14$193
This Kiwi.com deal was found by Cheapflights users on 12/14. 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.
Wed 12/311:29 pmSFO - DEN
1 stop8h 10mMultiple Airlines
Tue 1/63:46 pmDEN - SFO
1 stop9h 08mMultiple Airlines
Deal found 12/14$194
This Frontier deal was found by Cheapflights users on 12/14. 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 12/182:13 pmSFO - DEN
1 stop5h 07mFrontier
Thu 1/86:10 amDEN - SFO
Nonstop2h 53mFrontier
Deal found 12/14$196

Find 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 December 15, 2025.

Most accurate provider

CheapOair
3 stars

Most trusted provider

CheapOair
3 stars

Round-trip from

$92
(Kiwi.com)

One-way from

$62
(Trip.com)

Popular in

December

Cheapest in

January

Average price

$285
Provider with most accurate pricing for San Francisco-Denver Intl flight deals.
Search Deals
Provider most trusted by Cheapflights users for San Francisco-Denver Intl flights.
Search Deals
From San Francisco to Boulder
Search Deals
One-way flight from San Francisco to Boulder
Search Deals
Highest demand for flights based on searches. 0% potential increase in price ($0 potential increase over avg. RT price).
Search Deals
Cheapest flight prices on average. 1% potential price decrease ($5 potential savings vs. average RT price).
Search Deals
Average for round-trip flights in December 2025
Search Deals

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 December 15, 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

Sat 1/24

4:46 pm-11:35 pm

1 stop5h 49m

Denver Intl

Sat 1/31

12:34 pm-4:32 pm

1 stop4h 58m

$166

San FranciscoDenver

SFO - DEN

SFODEN

San Francisco

Wed 1/21

11:45 am-9:20 pm

1 stop8h 35m

Denver Intl

Wed 1/28

8:35 am-10:30 am

Nonstop2h 55m

$187

San FranciscoDenver

SFO - DEN

SFODEN

San Francisco

Tue 1/20

2:52 pm-11:58 pm

1 stop8h 06m

Denver Intl

Sun 1/25

7:00 am-5:59 pm

1 stop11h 59m

$189

San FranciscoDenver

SFO - DEN

SFODEN

San Francisco

Fri 2/20

6:30 am-6:56 pm

1 stop11h 26m

Denver Intl

Wed 2/25

6:45 pm-11:59 pm

1 stop6h 14m

$189

San FranciscoDenver

SFO - DEN

SFODEN

San Francisco

Fri 2/6

7:00 am-4:13 pm

1 stop8h 13m

Denver Intl

Sun 2/8

7:00 am-2:00 pm

1 stop8h 00m

$197

San FranciscoDenver

SFO - DEN

SFODEN

San Francisco

Sat 1/10

11:41 am-11:58 pm

1 stop11h 17m

Denver Intl

Mon 1/12

12:34 pm-4:32 pm

1 stop4h 58m

$209

San FranciscoDenver

SFO - DEN

SFODEN

San Francisco

Thu 2/19

6:30 am-5:20 pm

1 stop9h 50m

Denver Intl

Mon 2/23

6:45 pm-11:59 pm

1 stop6h 14m

$209

San FranciscoDenver

SFO - DEN

SFODEN

San Francisco

Wed 1/7

7:40 am-3:50 pm

2 stops7h 10m

Denver Intl

Sat 1/10

8:05 am-1:35 pm

1 stop6h 30m

$222

San FranciscoDenver

SFO - DEN

SFODEN

San Francisco

Thu 2/26

2:39 pm-11:25 pm

1 stop7h 46m

Denver Intl

Mon 3/2

6:40 am-1:48 pm

1 stop8h 08m

$223

San FranciscoDenver

SFO - DEN

SFODEN

San Francisco

Sat 1/31

2:35 pm-11:25 pm

1 stop7h 50m

Denver Intl

Mon 2/2

5:15 am-1:43 pm

2 stops9h 28m

$228

Flights are sorted by cheapest round-trip flights first.

Deals found on 12/15

Showing 1-10 of 20 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 December 12, 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 December 15, 2025.

It’s typically best to fly out from San Francisco to Boulder in the morning. Doing so could potentially save you 9% 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.

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 December 15, 2025.

The most flights from SFO to BD9 are scheduled on a Monday (51 on average). You will have fewer flight options on Thursday, which is when the least amount of flights are scheduled (5 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 December 15, 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
7.9
Good
4,250 reviews

Overall

7.9

Boarding

8.1

Food

7.0

Entertainment

7.5

Crew

8.6

Comfort

8.0

Reviews

1 / 20
2.0
Mediocre

Thomas,Dec 2025

SEA - DEN

Plane two hours late in leaving 1:00 pm west coat time got home next day at 2:45am most car rental places are closed and don’t open till 5am
Southwest
7.9
Good
4,250 reviews
Southwest
7.9
Good
4,250 reviews

Overall

7.9

Boarding

8.1

Food

7.0

Entertainment

7.5

Crew

8.6

Comfort

8.0

Reviews

1 / 20
2.0
Mediocre

Thomas,Dec 2025

SEA - DEN

Plane two hours late in leaving 1:00 pm west coat time got home next day at 2:45am most car rental places are closed and don’t open till 5am
United Airlines
7.4
Good
9,093 reviews
Southwest
7.9
Good
4,250 reviews

Overall

7.9

Boarding

8.1

Food

7.0

Entertainment

7.5

Crew

8.6

Comfort

8.0

Reviews

1 / 20
2.0
Mediocre

Thomas,Dec 2025

SEA - DEN

Plane two hours late in leaving 1:00 pm west coat time got home next day at 2:45am most car rental places are closed and don’t open till 5am
American Airlines
7.2
Good
11,048 reviews
Southwest
7.9
Good
4,250 reviews

Overall

7.9

Boarding

8.1

Food

7.0

Entertainment

7.5

Crew

8.6

Comfort

8.0

Reviews

1 / 20
2.0
Mediocre

Thomas,Dec 2025

SEA - DEN

Plane two hours late in leaving 1:00 pm west coat time got home next day at 2:45am most car rental places are closed and don’t open till 5am
Allegiant Air
7.2
Good
700 reviews
Southwest
7.9
Good
4,250 reviews

Overall

7.9

Boarding

8.1

Food

7.0

Entertainment

7.5

Crew

8.6

Comfort

8.0

Reviews

1 / 20
2.0
Mediocre

Thomas,Dec 2025

SEA - DEN

Plane two hours late in leaving 1:00 pm west coat time got home next day at 2:45am most car rental places are closed and don’t open till 5am
Frontier
5.8
Fair
3,082 reviews
Southwest
7.9
Good
4,250 reviews

Overall

7.9

Boarding

8.1

Food

7.0

Entertainment

7.5

Crew

8.6

Comfort

8.0

Reviews

1 / 20
2.0
Mediocre

Thomas,Dec 2025

SEA - DEN

Plane two hours late in leaving 1:00 pm west coat time got home next day at 2:45am most car rental places are closed and don’t open till 5am

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 35 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 285 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 Alaska Airlines and Southwest fly from San Francisco to Boulder in about 5h 49m. The time it takes to get you to your destination can typically vary by up to 2h 46m. 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 Frontier. According to our data, you can fly for as low as $34. Users have also found prices from $42 and $64 on Allegiant Air and Alaska Airlines, respectively.

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

    Consider Asiana Airlines (88%), United Airlines (87%) or Virgin Australia (87%) 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 $75. On average you can expect to pay $1,086. The most popular route, (San Francisco - Denver Intl), can usually be booked for $72.

  • 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

Browse thousands of different options on Cheapflights for your next trip

Toggle through the tabs below to find thousands of options on Cheapflights for your next trip.

Alternative routes for San Francisco to Boulder

See prices for flight routes from nearby airports that may be better suited for you.
Los Angeles to Denver flights
San Francisco to Denver flights
Ontario to Denver flights
Santa Ana to Denver flights
San Diego to Denver flights
San Jose to Denver flights
Las Vegas to Denver flights
Sacramento to Denver flights
Burbank to Denver flights
Los Angeles to Aspen flights
Fresno to Denver flights
Oakland to Denver flights
Reno to Denver flights
Los Angeles to Vail flights
San Francisco to Aspen flights
San Francisco to Vail flights
Palm Springs to Denver flights
Bakersfield to Denver flights
Los Angeles to Hayden flights
Medford to Denver flights
Santa Barbara to Denver flights
San Luis Obispo to Denver flights
Arcata to Denver flights
Long Beach to Denver flights
Monterey to Denver flights
San Francisco to Durango flights
Ontario to Aspen flights
San Diego to Hayden flights
Los Angeles to Colorado Springs flights
Los Angeles to Durango flights
Redding to Denver flights
Burbank to Aspen flights
Sacramento to Colorado Springs flights
Ontario to Vail flights
Los Angeles to Montrose flights
Santa Rosa to Denver flights
Ontario to Colorado Springs flights
Palm Springs to Colorado Springs flights
San Diego to Vail flights
San Francisco to Hayden flights
San Francisco to Montrose flights
Santa Ana to Aspen flights
San Francisco to Colorado Springs flights
San Jose to Colorado Springs flights
San Diego to Durango flights
Las Vegas to Colorado Springs flights
San Diego to Colorado Springs flights
Ontario to Durango flights
Los Angeles to Grand Junction flights
Santa Ana to Vail flights

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 December 15, 2025.
AirlineCheapestAverageFlexibilityOn-time
FrontierCheapest$68Average$188FlexibilityNo cancel feeOn-time62%
Allegiant AirCheapest$88Average$100FlexibilityNo cancel feeOn-time88%
SouthwestCheapest$157Average$347FlexibilityNo cancel feeOn-time63%
United AirlinesCheapest$163Average$378FlexibilityNo cancel feeOn-time69%
DeltaCheapest$175Average$280FlexibilityNo cancel feeOn-timeN/A
American AirlinesCheapest$176Average$428FlexibilityNo cancel feeOn-time71%

100% Free

Cheapflights is completely free to use, so you can start saving the moment you arrive.

Book with Flexibility

Our users can plan ahead with confidence and find flights with no change fees

Travel Smart

Millions of people come to us for their flight needs every year. We help make travel planning easy by providing useful insights and data-driven graphs that can inform your decisions.