Tides rise, and tides fall. Sometimes we sail by deep water, and six hours later the same place can be dry. You are going to need to know how much water is in a given place at a specific time in order to navigate safely – and the latest episode of Sail Ho! explains just how to do that.

You will need some basic information to begin your tidal height calculations. You can find this in a tide table, which gives you times for high water and low water, as well as the height of tide at each point. A tide table will look something like this:

Example of a tide table

Using this information, you can try one of two methods to calculate the height of tide in between.

The simplest method is the rule of 12ths. But in some places, such as the Solent, tides follow a very irregular pattern. For this reason, you have to know how to calculate height of tide using the appropriate tidal curve. You can see examples of regular and tidal anomaly curves below:

In other words, you can use a tidal curve for tidal calculations anywhere, but the rule of 12ths only works where there are no tidal anomalies, caused for example by islands that disrupt the flow of water. You will find tidal curves and tide tables in your almanac.

Watch our latest animated episode on the Sail Ho! YouTube channel to learn what the rule of 12ths is, and how to use a tidal curve. This sail training theory video is available in English and Polish – just click on the appropriate image below to view it in the language you prefer.

English versionPolish version

And, if you want to know more about what causes tides and how they work, watch our introduction to tides episode here.

Download a free, printable example of a regular tidal curve here, and use it to practice your skills using data from your local tide table – or any other of your choice.

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