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

Drift distance (nm)

Required number in nm. Distance the object drifted.

Elapsed time (h)

Required number in h. Time over which the drift was measured.

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

Compute the tidal stream rate from the distance a free-floating object drifted and the elapsed time. Inputs are interpreted exactly in the displayed units and the calculation returns the following fields without presentation rounding.

Tidal stream rate (kt)

Returned number in kt. Tidal stream rate in knots.

• 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.
• Drift distance 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.

• PHRF Time on Distance Calculator

  Compute a PHRF time-on-distance corrected time by subtracting the rating allowance over the course length from elapsed time.

• 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.

• Course to Steer With Current Calculator

  Compute the heading to steer that compensates for a known tidal stream to achieve a desired track.