From San Francisco airport
The easiest way to come from SFO to San Francisco is to use the BART. It will take you to the center of the city or East Bay.
There are 3 to 4 trains per hour and it takes about 30 minutes to connect the airport to the center of San Francisco. The BART station is located in the International terminal, departure level, side G.
If you arrive or depart for a domestic flight, use the SFO Airtrain shuttles which are free and will take you to the BART station.
Here is the Bart trip planner to help you.
Good to know:
– The schedules of the first trains change between weekdays and weekend
– All trains stop at midnight during weekdays and Saturdays, but at 9 pm on Sunday
– Children younger than 4 years old go free. Beware, BART no longer sells paper tickets. Every rider needs a Clipper card. There is a one-time $3 charge to purchase a Clipper card from a BART vending machine. You can avoid this fee by adding a new Clipper card to your digital wallet.
To give you an idea of the price, the return ticket between SFO and Powell St, in San Francisco costs around $19.30 round trip per adult
Please, find a fare calculator here
From Oakland Airport
Oakland Airport is also served by BART and the station is located in terminal 1, opposite the baggage belts. Whether you are traveling to Oakland or San Francisco, you will need to change trains at the Coliseum station.
All the details are on this page: https://bartable.bart.gov/latest-news/how-ride-bart-airport.
From San Jose Airport
It’s getting trickier… no direct connection between Caltrain or BART is available. It is possible as always but not very convenient https://www.flysanjose.com/public-transit.