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

Actual course over ground (°)

Required number in °. Course actually made good over the seabed during the leg.

Distance run (nm)

Required number in nm. Distance sailed along the actual track.

Elapsed time (h)

Required number in h. Time elapsed during the leg.

Intended course (°)

Required number in °. Course you intended to steer.

Speed through water (kt)

Required number in kt. Average speed through the water while steering the intended course.

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

Calculate current set and drift by subtracting the vessel's through-water velocity vector from its observed over-ground velocity vector. Inputs are interpreted exactly in the displayed units and the calculation returns the following fields without presentation rounding.

Set (°)

Returned number in °. Direction toward which the derived current flows; zero when the current vector has zero magnitude.

Drift (kt)

Returned number in kt. Magnitude of the derived current velocity vector.

• 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.
• Actual course over ground must be at least 0.
• Actual course over ground must be no greater than 360.
• Distance run must be at least 0.
• Intended course 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.

• Course Over Ground Calculator

  Calculate the resulting course over ground from vessel motion combined with current set and drift.

• Speed Over Ground Calculator

  Calculate the resulting speed over ground from vessel motion combined with current set and drift.

• Drying Height Clearance

  Compute the water depth over a charted drying patch by subtracting its drying height from the height of tide; a negative result means the patch remains exposed.