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

High water (m)

Required number in m. Height of the high water.

Hours from high water (h)

Required number in h. Hours elapsed since high water, between 0 and 6.

Low water (m)

Required number in m. Height of the low water.

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

Interpolate tide height on a cosine curve from heightM = lowWaterMeters + (highWaterMeters - lowWaterMeters) * (cos(PI * hoursFromHigh / 6) + 1) / 2. Inputs are interpreted exactly in the displayed units and the calculation returns the following fields without presentation rounding.

Tide height (m)

Returned number in m. Predicted tide height at the given time.

• 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.
• Hours from high water must be at least 0.
• Hours from high water 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.

• Tidal Curve Height

  Interpolate a falling tide from high water to low water with a cosine curve over the specified high-to-low interval.

• Bridge Clearance Calculator

  Compute the vertical margin under a chart-datum bridge clearance by subtracting both height of tide and vessel air draft.

• Corrected Depth Calculator

  Add the height of tide to the charted depth sounding to obtain the actual depth of water.