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

Vessel course

Required number.

Vessel speed

Required number.

Current set

Required number.

Current speed

Required number.

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

Calculate the resulting speed over ground from vessel motion combined with current set and drift. Inputs are interpreted exactly in the displayed units and the calculation returns the following fields without presentation rounding.

Speed over ground

Returned number.

• 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.
• Vessel course must be at least 0.
• Vessel course must be no greater than 360.
• Vessel speed must be at least 0.
• Current set 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.

• Set and Drift Correction Calculator

  Calculate current set and drift by subtracting the vessel's through-water velocity vector from its observed over-ground velocity vector.

• Crew Drift Estimate

  Estimate how far an overboard crew member drifts as current speed times time in the water plus wind speed times time scaled by a one percent windage coefficient.