The predictions on this website are sourced from the freely available “XTide” application by David Flater. Unfortunately for various reasons maintenance of updates for locations in the UK was ended in early 2012. As the harmonic constants are no longer being updated the accuracy of tidal predictions based upon them will decrease over time.

A legal notice about the source of the UK tide data can be found here:

The harmonic constants used to perform tide predictions for locations in the U.K. are derived from sea level data obtained from the British Oceanographic Data Centre (BODC) based at the The National Oceanography Centre, Liverpool, formerly the Proudman Oceanographic Laboratory.  The predictions are not the same as those computed by the National Oceanography Centre, which uses its own sets of harmonic constants.

The data were supplied by the British Oceanographic Data Centre as part of the function of the National Tidal & Sea Level Facility, hosted by the National Oceanography Centre and funded by the Department for Environment, Food and Rural Affairs and the Natural Environment Research Council.

The text of the letter from Proudman Oceanographic Laboratory granting permission and stating conditions for using the BODC data to derive harmonic constants is available at

The license agreement for the BODC data itself is available at  Please note that none of the BODC data has been redistributed.  Only harmonic constants derived from that data have been made available.

Please note: This tide data is provided with no warranty or accuracy claims and represents an approximation of potential tide heights. It should not be used for any safety or critical navigation purposes!

UK Hydrographic Office Data

Although the tide tables published on this website have already drifted from the official published Admiralty Tide Tables, the variation is not currently too bad. We are monitoring the situation and if the difference becomes unreasonable then we will look for an alternative solution. Unfortunately the cost of licensing the ‘official’ tide tables is too great at this time for a site that is being provided as a free resource.