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

Forward speed (m/s)

Required number in m/s. Forward speed through the water.

Lateral drift (m/s)

Required number in m/s. Lateral drift speed caused by current or leeway.

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

Compute the rudder correction angle from correctionDeg = degrees(atan(lateralDriftMs / forwardSpeedMs)). Inputs are interpreted exactly in the displayed units and the calculation returns the following fields without presentation rounding.

Correction angle (deg)

Returned number in deg. Course correction angle to hold the desired track.

• 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.
• Forward speed must be at least 0.
• Lateral drift 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.

• Vang Angle Calculator

  Compute the vang angle in degrees as atan of the mast attachment height over the boom attachment distance.

• Bowsprit Compression Load

  Compute the ideal axial compression required to balance a forestay load at a specified angle to the deck.

• Current Correction Angle Calculator

  Compute the signed crab angle needed to oppose a current's cross-track component. Routes whose cross-current exceeds boat speed cannot be held.