The Rule of Twelfths provides an approximate tide height change by which unit of time?

• A. Day
• B. Hour
• C. Minute
• D. Second

Answer: (B)

The Rule of Twelfths is a quick, practical way to estimate how much the tide will rise or fall during the rising or falling tide over the first six hours. It splits the total height change into hourly portions so you can gauge what the water level will be each hour. Since the change is tracked in hours, the unit of time you’re dealing with is the hour. For example, if the total tide change is six feet, you’d expect about 0.5 ft in the first hour, 1 ft in the second, 1.5 ft in the third, another 1.5 ft in the fourth, 1 ft in the fifth, and 0.5 ft in the sixth. This is a rough guide and can vary with wind, pressure, and local coastline features, but it’s a handy rule of thumb for planning paddling and recognizing currents and depth changes on coastal Maine trips.