What does the Rule of Twelfths help estimate in tidal planning?

• A. Wave height at the shore
• B. Estimate tide height between highs and lows
• C. Forecast air temperature
• D. Predict wind direction

Answer: (B)

The idea behind this rule is to have a quick, practical way to estimate how high the water will be as a tide comes in or goes out, without needing a full tide chart. The tide’s rise (or fall) isn’t perfectly linear, but it tends to follow a recognizable pattern over the six hours between low and high tide: about a twelfth, then two twelfths, then three twelfths, then three twelfths again, then two twelfths, and finally one twelfth of the total range. Put another way, you start at the low water and add those fractions of the total tidal range as time passes; after six hours you’ve added the whole range and reached high water. This lets you estimate, for any given hour after low tide (or after high tide), roughly how deep the water will be in shallow channels or at exposed ledges—very handy for planning paddling routes in Maine’s tidal waters.

Keep in mind it’s a rough rule of thumb, not a precise measurement. Wind, barometric pressure, and local shallow areas can push actual depths away from the estimate, so use it alongside real tide tables and local observations for safer planning.