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Tidal Coefficients

Tidal coefficients is a system primarily used in France and therefore featured in many French pilot books, web sites and harbour notices. Its a tabular system that depicts the 'size' or 'magnitude' of the expected tide at a simple glance. It eliminates the need of having to look up and calculate the range of tides and the need to determine whether its neaps or springs or anywhere in between. The coefficients usually range from anywhere between 20 and 120 and a good typical guide to use is:

20 – very small neap
45 – mean neap
70 – average tide
95 – mean spring
120 – very big spring

As an example of its uses, suppose the sill at some French Marina opens at HW±2 when the coefficient is greater than 70. This means that with an average sort of tide, that’s when you can expect to enter. It follows therefore that if the tide coefficient tends towards the neap spectrum, the marina gate will open later. The coefficient can also be used as a guide for tidal stream rates.

The coefficient tables are valid for all areas featured in SailingAlmanac.