Cheapest Day to Buy Flights from Boston to San Francisco
Boston to San Francisco is 4,341 km (2,697 mi) great-circle — commonly 8–12 h nonstop or with 1 stop. Fares typically bottom out 3–12 weeks before departure; the calendar below shows the cheapest price for every day of the next 12 months.
Check live prices on Aviasales ↗Low Fare Calendar — Boston to San Francisco
When to book vs. when to fly — Boston → San Francisco
Live data from recent Aviasales searches for BOS → SFO, plus a booking rule of thumb.
Lowest indicative per-adult round-trip fares seen in Aviasales searches — confirmed live on the booking site before payment.
See the cheapest month’s fares ↗Search any date — Boston → San Francisco
Flight options — Boston → San Francisco
Recently-seen round-trip fares — click any flight for details, alternatives and booking.
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FAQ — BOS → SFO
How much is a flight from Boston to San Francisco?
Prices vary by season and departure day. The Low Fare Calendar on this page shows the cheapest fare for every day of the coming year between Boston (BOS) and San Francisco (SFO).
Which airlines fly from Boston to San Francisco?
The Boston → San Francisco route covers about 4,341 km and commonly 8–12 h nonstop or with 1 stop. Multiple carriers operate it — search FlyTiming to compare every airline and agency serving BOS → SFO in one search.
What is the cheapest day to fly from Boston to San Francisco?
It varies by month. The price card on this page highlights the cheapest month and the historically cheapest day of the week to fly this route — the Low Fare Calendar below marks low-fare days in green.
When is the best time to book flights from Boston to San Francisco?
As a rule of thumb, fares on international routes are usually lowest roughly 3–12 weeks before departure — and northern-summer peak (June–August) usually means the highest fares — book early or aim for the shoulder months. The calendar below is the fastest way to spot the cheapest months for Boston → San Francisco.