The required rode length depends on water depth, tide range, freeboard, and weather. Multiply the total depth (water + tide + freeboard) by the scope ratio: 5:1 for calm conditions, 7:1 for moderate wind, and 10:1 for storms.
- Total depth = water depth + tide range + bow height (freeboard)
- Calm weather: 5:1 scope — 15 ft depth × 5 = 75 ft of rode
- Moderate wind: 7:1 scope — 15 ft depth × 7 = 105 ft of rode
- Storm conditions: 10:1 scope — 15 ft depth × 10 = 150 ft of rode
- All-chain rode can use lower scope ratios than chain+rope combinations
| Depth (ft) | Calm (5:1) | Moderate (7:1) | Storm (10:1) |
|---|---|---|---|
| 10 ft | 50 ft | 70 ft | 100 ft |
| 15 ft | 75 ft | 105 ft | 150 ft |
| 20 ft | 100 ft | 140 ft | 200 ft |
| 30 ft | 150 ft | 210 ft | 300 ft |