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

Righting arm (ft)

Required number in ft. Horizontal distance from centerline to center of gravity; negative values represent a capsize moment.

Displacement (lb)

Required number in lb. Displacement of the vessel.

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

Compute the righting moment in pound-feet as righting arm times displacement; a negative arm yields a capsize moment. Inputs are interpreted exactly in the displayed units and the calculation returns the following fields without presentation rounding.

Righting moment (lb·ft)

Returned number in lb·ft. Righting moment; negative values indicate capsize moment.

• 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.

• Horizon Dip Calculator

  Compute the dip of the visible horizon in minutes of arc as the coefficient zero point nine seven times the square root of height of eye in feet.

• Horizon Distance Calculator

  Compute the distance to the visible horizon in nautical miles as the coefficient one point one seven times the square root of eye height in feet.

• Horizon Range Calculator

  Compute the distance to the visible horizon in nautical miles as one point one seven times the square root of the observer height in feet.