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

SL length (m)

Required number in m.

SMW width (m)

Required number in m.

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

Estimate the symmetric spinnaker area from the SL leech length and SMW width using the standard three-quarter approximation. Inputs are interpreted exactly in the displayed units and the calculation returns the following fields without presentation rounding.

Spinnaker area (m²)

Returned number in m².

• 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.

• Sail Load Calculator

  Estimate the aerodynamic load on a sail from wind speed and sail area using a flat-plate drag model.

• Anchor Circle Radius Calculator

  Estimate the maximum anchor-to-bow radius from water depth and rode scope. Add the vessel length when checking the full area swept by the stern.

• Chain Catenary Sag Calculator

  Estimate the catenary sag of anchor chain between two points from its weight per meter, span, and horizontal tension using a parabolic approximation.