No. | Mean Wave Height in Feet | Sea Description |
| 0 | - | Calm |
| 1 | - | Ripples with the appearance of scales formed but without foam crests |
| 2 | 0.5 | Small short wavelets. Crests have a glassy appearance but do not break |
| 3 | 2 | Large wavelets. Crests begin to break with a little foam. Perhaps some scattered white horses |
| 4 | 3.5 | Small waves becoming longer. Fairly frequent white horses |
| 5 | 6 | Moderate pronunced long waves. Many white horses with the chance of some spray |
| 6 | 9.5 | Large waves begin to form. White foam crests are more extensive everywhere with the probability of spray. |
| 7 | 13.5 | Sea heaps up with white foam from breaking waves. Spindrift begins to be seen. |
| 8 | 18 | Moderately high waves of greater length; edges of crests break into spindrift. Foam blown into well-marked streaks |
| 9 | 23 | High waves with some dense streaks of foam Crests begin to roll over. Spray may affect visibility |
| 10 | 29 | Very high waves with long overhanging crests. Great patches of foam in dense white streaks. Sea surface is white.Tumbling of sea becomes heavy. Visibility affected |
| 11 | 37 | Exceptionally high waves. Small and medium sized ships may be lost to view. Sea completely covered with foam. Edges of wave egess blown into froth. Visibility affected |
| 12 | 45+ | Sea completely white with driving spray. Air filled with foam and spray. Visibility very seriously affected. |