Anchor Scope Calculator
Work out the right anchor scope and rode length for depth, tide and chain-vs-rope ratio with this free anchoring calculator in your browser.
100% FreeRuns in your browserBasic
Enter Values
Minimum 0
Enter your values and press Calculate to see results.
How to use this calculator
- Enter the water depth at high tide and your bow roller height.
- Set the scope ratio.
How it works
Rode = (depth + bow height) × scope ratio. 5:1 is typical for chain, 7:1+ for rope or rough weather.
Worked example
5 m depth, 1.5 m bow, 7:1. = 45.5 m of rode.
Common mistakes
- Using depth alone — add the bow height above the water.
- Forgetting to allow for the tide rising.
Frequently asked questions
What scope ratio should I use?
Around 5:1 for all-chain in calm conditions; 7:1 or more for rope rode or heavy weather.
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Cite this tool
Zerdly. (2026). Anchor Scope Calculator. Retrieved from https://www.zerdly.com/tools/anchor-scope-calculator/
Tip: Enter any known values to calculate the remaining results.
Designed to run locally in your browser. Tool inputs are not intentionally stored by Zerdly unless stated otherwise.