About San Francisco Tides

sftides.com is a free, no-frills page for people who need to know what the water is doing around San Francisco Bay and the Delta today: when the tide is high and low, when the current is running its hardest, when it goes slack, and when the sun and moon rise and set. It loads fast, works on a phone, and needs no account.

What it shows

• Tides – every high and low tide of the day, with the height in feet above mean lower low water (MLLW), the same reference NOAA uses on its charts.
• Currents – the strongest flood and ebb of the day with their speed in knots, and the slack-water times, where a current is predicted for that location.
• Sun and moon – sunrise, solar noon, sunset, the moon phase and the next full and new moon.
• Any day for the next 100 days – pick a date from the list, then a location from the list or from the chart of locations. The address in your browser remembers the choice, so you can bookmark it.

Where the numbers come from

The tide and current predictions are NOAA's. Each year the site loads NOAA's published predictions for a set of base stations:

• Tides: San Francisco / Golden Gate (9414290), Port Chicago (9415144), Antioch (9415064), Crockett (9415143), Hunters Point (9414358), Pinole Point (9415056), San Mateo Bridge (9414458) and Wards Island (9415105).
• Currents: San Francisco Bay Entrance (SFB1201), Carquinez Strait (SFB1319) and Vulcan Island (PCT0936).

The other locations are worked out exactly the way NOAA publishes its secondary stations: from a base station, shifted by NOAA's own time difference and adjusted by NOAA's own height difference or height ratio. The site's numbers are compared against NOAA's own predictions for every location as part of its automated testing, so a typo or a stale table does not go unnoticed.

The chart

The chart of locations shows each location at the position of its NOAA station, on NOAA's own electronic navigational chart, drawn on request by NOAA's Chart Display Service. It is only for finding a place and is not for navigation.

Sun and moon

Sunrise and sunset are calculated in your browser from the date and the latitude and longitude of the location, and agree with NOAA's and the U.S. Naval Observatory's tables to within a couple of minutes. The moon phase uses the true times of new moon, first quarter, full moon and last quarter, not an average lunar month, so the dates of the full and new moons are right. All times are Pacific time, with daylight saving applied, whatever time zone your device is set to.

How accurate is it, and what it is not

These are predictions, calculated from astronomy and from long records of the local water. They are not observations. Wind, barometric pressure, heavy rain and snowmelt (especially in the Delta in winter and spring) can raise or lower the water and speed up or slow down the current compared with the prediction. Do not use this site as your only source for navigation or safety decisions. Check NOAA's official tide tables and current charts, and the Coast Pilot, and use your own judgment on the water.

Learn why

If you have wondered why there are two tides a day, why slack water does not line up with high tide, or why you can ride a flood up the Bay but not an ebb back down, the articles explain it in plain language.

Who runs it

sftides.com is a personal project, built and maintained by Brent Bilger. It is free to use; advertising may be shown to help cover the cost of running it. See the privacy policy for what the site records and which cookies it uses, or get in touch with corrections and suggestions.