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Anchor Rode Length Calculator
Compute recommended anchor rode length from water depth, freeboard/bow height, and tide allowance using standard scope ratios for calm and heavy-weather anchoring.
🔒 This tool runs entirely in your browser. Your files are never uploaded to a server.
Total depth to seabed + bow height: —
Calm weather (5:1)
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Typical overnight (7:1)
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Heavy weather (10:1)
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Scope is the ratio of rode length to total depth (water depth + bow height + tide rise). All-chain rode can typically use a slightly lower scope than rope/chain combinations.
How the Anchor Rode Length Calculator works
- Enter the charted water depth, your bow height above the water, and how much the tide will rise before you plan to leave.
- These add together to give the total effective depth the rode must span.
- The tool multiplies that depth by standard scope ratios — 5:1 for calm conditions, 7:1 for typical overnight anchoring, and 10:1 for heavy weather — to recommend a rode length for each scenario.
FAQ
What is "scope" in anchoring?
Scope is the ratio of anchor rode length paid out to the total depth from the bow roller to the seabed. A higher scope pulls the anchor shank flatter against the bottom, which greatly improves holding power.
Why include bow height and tide rise in the depth calculation?
The rode has to reach from the bow (above the waterline) down to the seabed, so bow height adds to the effective depth. Tide rise matters too — if you anchor at low tide, the water (and required rode) will be deeper by the time high tide arrives.
Why does heavy weather need more scope?
A higher scope ratio (closer to 10:1) keeps more strain on the rode horizontal rather than vertical, which is what keeps the anchor set during strong wind or wave action — at low scope, a hard gust can pull the anchor up and out of the bottom.
How we compare
| Feature | Online Tool Store | Cruising guide rule of thumb | Guessing by eye |
|---|---|---|---|
| Accounts for tide rise automatically | ✓ | ✗ | ✗ |
| Multiple weather scenarios at once | ✓ | ✗ | ✗ |
Always cross-check against your local swing room, seabed type, and current chart depth before setting anchor — these are general guideline ratios, not a substitute for local knowledge.