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

Wind speed (kn)

Required number in kn. Sustained wind speed.

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

Estimate deep-water significant wave height for a fully developed sea as 0.21 U²/g, converting the supplied wind speed from knots to meters per second. Inputs are interpreted exactly in the displayed units and the calculation returns the following fields without presentation rounding.

Significant wave height (m)

Returned number in m. Significant wave height for a fully developed sea.

• 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.
• Wind speed 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.

• Douglas Sea State Lookup

  Look up the Douglas sea state from zero to nine for a significant wave height in meters using standard inclusive upper bounds.

• Wave Period Estimate

  Estimate the peak period of fetch-limited deep-water waves from wind speed and unobstructed fetch using the dimensionless SMB growth relation.

• Beaufort Scale Lookup

  Look up the Beaufort wind force from zero to twelve for a wind speed in knots using standard inclusive upper bounds.