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

Spring range (m)

Required number in m. Spring tidal range at the location.

Maximum rate (kt)

Required number in kt. Fastest tidal stream rate expected.

Depth (m)

Required number in m. Water depth over the shallows.

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

Estimate the severity of overfalls from the spring tidal range, maximum stream rate, and water depth. Inputs are interpreted exactly in the displayed units and the calculation returns the following fields without presentation rounding.

Overfalls risk factor

Returned number. Dimensionless indicator of overfall severity.

• 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.
• 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 Race Speed Calculator

  Scale the published peak spring stream rate to the day's tidal range to estimate the speed of a tidal race.

• Anchor Circle Radius Calculator

  Estimate the maximum anchor-to-bow radius from water depth and rode scope. Add the vessel length when checking the full area swept by the stern.

• Tidal Stream at Time Calculator

  Model the tidal stream as a sinusoid and return its signed rate at a given time into the flood-and-ebb cycle.