Tidal Current Calculator
Estimate current speed using Rule of Twelfths
Current Data
From tide tables or current atlas
Time Since Slack Water
Passage Planning
Current Analysis
Current Speed Now
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Tide Stage
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Speed Over Ground
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Current Effect
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% of Max Current
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Rule of Twelfths
| Hour | Twelfths | % of Max | Cumulative |
|---|---|---|---|
| 1st | 1/12 | 8% | 8% |
| 2nd | 2/12 | 17% | 25% |
| 3rd | 3/12 | 25% | 50% |
| 4th | 3/12 | 25% | 75% |
| 5th | 2/12 | 17% | 92% |
| 6th | 1/12 | 8% | 100% |
Tidal current follows approximately sinusoidal pattern, with maximum flow at mid-tide.