⚓️ The clock that invites you to dream ⛵️

The rule of twelfths, the calculation of tides

How does the rule of twelfths work for calculating the tide? The rule of twelfths is a method used to estimate the tide level at a given time in an area where tides are regular. Here's how it works:
  • Tidal cycle: Tides follow a regular cycle that is usually based on the lunar cycle. This complete cycle includes two high tides and two low tides per day, with a period of approximately 24 hours and 50 minutes for semi-diurnal tides (see the tides page )
  • Division into twelfths: To simplify the calculation, we divide this cycle into 12 equal periods called "twelfths".
  • Estimating Tide Height: The tide clock can be used to find out the tide height at certain key times of the day, such as high or low tides.
  • Interpolation: Using the rule of twelfths, we estimate the height of the tide at a specific time by interpolating between the values given for the nearest high and low tides. For example, if the high tide is 6 meters at 6am and the low tide is 2 meters at 12pm, at 9am (i.e. 3 twelfths into the cycle), we could estimate that the height of the tide is halfway between 6 and 2 meters, or about 4 meters.
  • Adjustments: It is important to note that this method provides rough estimates and may require adjustments to account for local factors such as currents, winds and weather conditions.

In summary, the rule of twelfths is a simple and convenient method for estimating the height of the tide at a given time by dividing the tidal cycle into 12 equal periods and interpolating between the known high and low tide values.