If your weekend budget is already feeling squeezed, San Francisco has an unusually strong answer from October 16 through 18: leave the wallet mostly alone and go outside.

There are free San Francisco events spread across the city, from Fort Mason and Mission Bay to Potrero Hill, the Mission and the Excelsior.

Here are seven worth putting on the calendar.

Friday: Fort Mason Night Market.

Start the weekend at Fort Mason Center, where the Friday night market brings food, vendors and an easy waterfront atmosphere together beginning at 5 p.m.

Entry is free, although your self-control around the food vendors may determine how inexpensive the evening remains.

Friday: Sundown Cinema at Crane Cove Park.

Pack a blanket for an outdoor screening of the 1988 comedy Beetlejuice at Crane Cove Park, scheduled for Friday evening.

The waterfront setting makes this one of those events where arriving early is part of the experience.

Saturday: Bay Area Science Festival Discovery Day.

UCSF Mission Bay hosts more than 125 hands-on science experiences from 11 a.m. to 4 p.m., making this an especially good option for families and anyone who prefers experiments to errands.

Saturday: Potrero Hill Festival.

Head to 20th Street for a neighborhood festival that turns the day into a community gathering with entertainment, local organizations and plenty of reasons to linger.

Saturday: Brava! Block Party.

On 24th Street in the Mission, Brava Theater celebrates the historic building’s 100th anniversary with live performances, DJs, art activities and film screenings.

It is free, family-friendly and a pretty good excuse to make an afternoon of the Mission.

Saturday: Hunters Point Shipyard Open Studios.

Artists at the Hunters Point Shipyard open their studios over the weekend, while the historic gantry crane becomes part of a large-scale light, video, sound and performance installation Friday and Saturday evening.

Sunday: Sunday Streets Excelsior.

The weekend finishes with nearly a mile of Mission Street closed to cars between Geneva Avenue and Theresa Street from 11 a.m. to 4 p.m.

The Sunday Streets Excelsior season finale includes family activities, a clothing swap, neighborhood gathering zones, coffee, a lucha libre showcase and plenty of room to walk, roll or simply wander down the middle of the street.

That is the real theme of this weekend: San Francisco’s neighborhoods become the entertainment.

You could easily spend all three days moving between events without buying a ticket.

Food, transit and spontaneous purchases are another matter, because this is still San Francisco.

But for the actual entertainment, the price is hard to beat.

Pick one neighborhood you rarely visit, give yourself a few hours, and let the city provide the itinerary.