How to Use the Wave Height & Sea State Checker
Enter the current or forecast wave height in feet, and this tool shows the corresponding international Douglas sea state grade along with a rough risk level for boating, fishing, or beach activity. Use it as a quick reference before planning time on the water.
The Douglas sea state scale classifies ocean conditions from state 0 (calm) to state 9 (phenomenal) based on significant wave height — the average height of the largest one-third of observed waves. Under about 0.3 ft, the surface is nearly glassy; around 4-8 ft (moderate to rough), small craft are generally advised to stay ashore.
Wave height alone doesn't tell the whole story. Wave period, wind speed and direction, current strength, and coastal shape can all make the same wave height feel very different in practice. Treat this tool as a general reference only, and always check official NOAA or Coast Guard marine forecasts before heading out on the water.
Frequently Asked Questions
It follows the international Douglas sea state scale (0-9), based on significant wave height — the average height of the tallest one-third of observed waves.
Yes — wave period, wind speed, and current can all change the actual danger level even at the same wave height. Treat this as a general reference and always check official marine forecasts before heading out.