Rule of twelfths 2

To find the times, heights and range of the tide it is necessary to consult the tide tables.
Let’s use the “Rule of Twelfths” for the port of Portsmouth on the 1st of November.
The first high water is at 00:45 UTC and the height of tide is 4.0 meters.
The next low water will be at 05:52 with a height of tide of 0.5 meters.
Now we calculate the range by subtracting the high water from the low water.
In our case 4.0 meters minus 0.5 meters equals 3.5 meters.
Dividing the range by 12 gives us a unit for our calculation – 3.5 meters divided by 12 equals 0.33 meters.