Wave Height Calculator

Estimate ocean wave heights based on wind speed and fetch length.

1. Wind Conditions
Wind Speed 20 Knots
2. Fetch Length

Distance the wind has blown over open water.

Fetch Distance 50 NM
Significant Wave Height (Hs)
4.8 ft
1.46 m Height (Meters)
4.2 s Wave Period
Moderate Sea

How are Ocean Waves Calculated?

The size of an ocean wave generated by wind depends on three primary factors:

  • Wind Speed ($U$): How fast the wind is blowing. Stronger winds transfer more energy into the water.
  • Fetch ($F$): The uninterrupted distance of open water over which the wind blows in a single direction. A long fetch allows waves to compound and grow larger.
  • Duration: How long the wind has been blowing. (This calculator assumes the wind has blown long enough to reach fetch-limited conditions).

Significant Wave Height ($H_s$): This is the standard measurement used by meteorologists and sailors. It represents the average height of the highest one-third of the waves. It closely matches what a trained observer would visually estimate the wave height to be.

Note: This tool uses a simplified JONSWAP/SMB fetch-limited formulation. Real ocean conditions involve complex interactions of swell, currents, and bathymetry.