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

Peak stream (kt)

Required number in kt. Peak stream rate at maximum flood.

Half period (h)

Required number in h. Hours from slack to the next slack, about 6.2 for semidiurnal tides.

Hours into cycle (h)

Required number in h. Elapsed hours since the cycle's slack-water start.

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

Model the tidal stream as a sinusoid and return its signed rate at a given time into the flood-and-ebb cycle. Inputs are interpreted exactly in the displayed units and the calculation returns the following fields without presentation rounding.

Tidal stream (kt)

Returned number in kt. Signed stream rate, positive on the flood lobe and negative on the ebb lobe.

• 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.
• Peak stream must be at least 0.
• Half period must be at least 0.
• Hours into cycle must be at least 0.
• 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 Stream Rate Calculator

  Compute the tidal stream rate from the distance a free-floating object drifted and the elapsed time.

• Overfalls Risk Factor

  Estimate the severity of overfalls from the spring tidal range, maximum stream rate, and water depth.

• 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.