Rule of Twelves Tide Calculator

With Keel input for Sailing and Sailboats

Knowing the Rule of Twelves is extraordinarily helpful for sailors to plan for safe passage with tides, whether that’s planning for the depth at a location or planning for tidal currents.  For a more in depth (haha) explanation, read Tides and the Rule of Twelves or take NauticEd’s online Coastal Navigation course.

NauticEd’s Rule of Twelves calculator displays the tidal height in 12ths, including when it is safe to make passage based upon the data inputted. Designed by and for sailors, the calculator includes input for a sailboat’s keel and safety margin depth.

To use the Rule of Twelves tide calculator, input:

  • Low and High Tides for the targeted time.
  • The Chart Datum.
  • Your Draft, or rather your keel depth + a margin of safety.

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Tides and understanding the Rule of Twelves

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Tides are often intimidating to sailors, but understanding tides can be made simple with the Rule of Twelves.

My vision for NauticEd is to provide the highest quality sailing and boating education available - and deliver competence wherever sailors live and go.
Grant Headifen
Last updated on October 9th, 2023