# 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.

### Tide Calculation Pop Quiz

Tide Calculation Pop Quiz - here's are a quick few tidal problems for you to solve.

### How to solve a tide height using the rule of twelves

Here is a tide curve plot for any tides that follow the rule of twelves. None do exactly, but it can provide a rough approximation.

### Can you solve this tidal problem?

In this sailing exercise, you'll be given a tidal problem. See if you have what it takes to solve it, or if you need a little more practice.

### Tides and the Rule of Twelves

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

Last updated on October 9th, 2023