Use this sailing calculation for planning or education when the vessel, units, reference directions, environmental conditions, and assumptions are explicitly known.

Hour into tide

Required integer. Tidal hour being evaluated, from the first through sixth hour after slack water.

Tidal range (m)

Required number in m. Total tidal range between low and high water.

The cited overview of Tide supplies background for the terminology and domain context used by this tool.^[1]

Compute the water level change for one hour of a tide using the rule of twelfths over a six hour half cycle. Inputs are interpreted exactly in the displayed units and the calculation returns the following fields without presentation rounding.

Height change (m)

Returned number in m. Water level change during that hour; positive toward high water.

• Vessel design and loading, sea state, wind, current, tide datum, weather, chart accuracy, equipment, crew, and safety margins can make real conditions differ from a simplified result.
• Hour into tide must be at least 1.
• Hour into tide must be no greater than 6.
• Use finite inputs in the displayed units, preserve source measurements and assumptions, and independently verify consequential decisions.

Cross-check current charts, tide and weather services, instrument data, vessel manuals, and applicable navigation rules, and retain a conservative alternative plan.

• Drying Height Clearance

  Compute the water depth over a charted drying patch by subtracting its drying height from the height of tide; a negative result means the patch remains exposed.

• Lock Water Volume Calculator

  Compute the volume of water moved by a lock filling or emptying as the chamber length times width times the water level change.

• Sound Signal Range

  Estimate the audible range of a vessel sound signal from its whistle output level in decibels using two nautical miles above one hundred and thirty decibels, one nautical mile above one hundred and ten, and half a nautical mile otherwise.