Tide Height - Rule of Twelfths

Approximate tidal height at any hour between LW and HW using the rule of 1-2-3-3-2-1 twelfths of the range.

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This calculator requires JavaScript to compute its result. The formula, symbols, and regulatory sources are shown in the Formula section below.

Formula, assumptions, and limits

\text{Fraction of range} = \{\tfrac{1}{12}, \tfrac{2}{12}, \tfrac{3}{12}, \tfrac{3}{12}, \tfrac{2}{12}, \tfrac{1}{12}\}

Symbol	Meaning	Unit
$HW$	High water height	m
$LW$	Low water height	m
$Range$	HW − LW	m
$Fraction$	Hours since LW → fraction of range

Source: Admiralty Tide Tables - NP 201

Approximate tidal height at any hour between LW and HW using the rule of 1-2-3-3-2-1 twelfths of the range.