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

New mean heading (°)

Required number in °. Mean heading after the shift.

Old mean heading (°)

Required number in °. Mean heading before the shift.

Elapsed time (min)

Required number in min. Minutes elapsed between the two mean headings.

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

Compute the signed rate of the shortest compass-direction change between two mean wind headings, correctly handling the wrap across north. Inputs are interpreted exactly in the displayed units and the calculation returns the following fields without presentation rounding.

Shift rate (°/min)

Returned number in °/min. Signed heading change per minute.

• 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.

• Oscillation Amplitude

  Compute half the shortest circular separation between the two extreme compass headings, including oscillations that cross north.

• Current Shear Gain

  Compute the signed current shear across the boundary between the near surface layer and the deeper layer as the near surface speed minus the deeper layer speed.

• Favored Tack From Shift

  Determine the favored tack from a signed wind shift where a positive shift lifts the starboard tack and a negative shift lifts the port tack.