I am looking for the "Lunitidal interval" for San Francisco, CA. I
need it for a new watch I purchased that is supposed to tell me what
the tides are doing in the Bay. Here's a website that tells you how to
compute the Lunitidal Interval" Now I need someone to do the math.

Here's the website for reference: 

http://tidesandcurrents.noaa.gov/faq2.html#22

The Lunitidal Interval will vary depending on your exact location; the web site

(The second listing is a hand-attempt to make the link appear
correctly. That attempt may or may not work.)

http://140.90.121.76/data_retrieve.shtml?input_code=100301000acc

<a href="//140.90.121.76/data_retrieve.shtml?input_code=100301000acc">http://140.90.121.76/data_retrieve.shtml?input_code=100301000acc</a>

shows 30 different stations in the Bay Area; the results depend on
where you are observing the tide.

For the first two locations, I get

"San Francisco, San Francisco Bay"
Lunitidal Interval for high tides: -0.92 (or 11.5 if your watch
requires positive numbers)
Lunitidal Interval for low tides: -7.60 (or 4.82 for a positive number)

"Pier 22 1/2, San Francisco, CA"
Lunitidal Interval for high tides: -0.52 (or 11.90)
Lunitidal Interval for low tides: -7.14 (or 5.28)

Assuming that I've done everything correctly, the difference between
the two San Francisco locations is 24 minutes for the high tide and 28
minutes for the low tides.

Note: I did not double-check these calculations, since you may want to
know the tide times at another of the locations. However, I suspect
that you just want to know generally when the tide is high and low.

There should be a high tide at the Golden Gate at around 4 pm today
and a low tide at about 11 pm. See the graph at:

http://sfports.wr.usgs.gov/cgi-bin/TS-Plot.cgi?Stname1=GG&Sta1=211&Stname2=GG&Sta2=214&FRAMED=map

This map has the same station number as used for the first calculation
above (high tide: -0.92; low tide: -7.60). If I've done everything
correctly, these numbers should give you the tide times shown in the
graph.