Anchor Scope & Holding Calculator checks whether deployed rode meets scope requirement and estimates a holding confidence score from scope, wind, and bottom type. It is useful for quick anchorage setup review when selecting rode length and judging relative holding robustness. The score is a planning heuristic, not a certified holding-force calculation. Use it to support anchoring decisions and combine with local seamanship practice and watchkeeping.
Use this calculator as one part of a broader passage-planning workflow. The
Marine Navigation Calculators toolkit
explains how CPA/TCPA, UKC, tide windows, route distance, set and drift, fuel range, and manoeuvring checks fit together.
You can also browse the full
Marine & Navigation category.
Enter the vessel, route, tide, current, or clearance assumptions exactly as labelled, then verify the result against official data and onboard judgment.
How to use this tool
Enter depth, bow roller height, desired scope ratio, and deployed rode length.
Add wind speed and select seabed type, then run assessment.
Confirm scope requirement status and review holding score before final anchor setup.
Anchor Inputs
Result
Required rode: 50.00 m
Rode margin: 5.00 m
Recommended scope for wind: 7.0:1
Scope requirement met: Yes
Holding score: 45.2/100
Formula or method
Required rode is estimated from water depth plus bow-roller height multiplied by desired scope ratio.
Holding confidence is a heuristic that considers scope adequacy, wind severity, and bottom type.
It is not an anchor-load simulation and does not certify holding safety.
Worked example
Checking evening anchorage setup
Depth: 5 m
Bow roller height: 1 m
Desired scope: 5:1
Rode deployed: 35 m
Wind: 18 kn
Bottom: sand
Result: Required rode is 30 m, so 35 m meets the entered scope target before other local factors are considered.
The result supports setup review, but swing room, gusts, tide, bottom condition, anchor type, and watchkeeping still matter.
How to interpret the result
Use scope output as anchoring planning support, not as a guarantee that the anchor will hold.
The required rode is 50 m, leaving a rode margin of 5 m.
The recommended scope is 7:1 and the holding score is 45.2 / 100.
Treat the score as planning support only and verify with seabed, weather, tide, swing room, and local practice.
Common mistakes
Using charted depth without tide or bow-roller height.
Ignoring swing radius and nearby vessels or hazards.
Treating a holding score as a substitute for setting technique and anchor checks.