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Marine & Boating Calculators

Anchor Scope Calculator

Anchor rode to let out for a given depth, with the scope ratio and swing circle.

Enter values

Results update as you type.

Result

Rode to let out

46 m

Measure depth from the bow roller, not the waterline, and always allow for the tide coming in.

In feet
150.9
Total vertical distance
9.2 m
Scope ratio
5 : 1
Swing radius
56 m
Swing circle diameter
112 m
Swing area
9,852 m²

About the Anchor Scope Calculator

Anchor rode to let out for a given depth, with the scope ratio and swing circle.

Also known as: anchor rode calculator, scope ratio, how much chain to let out, anchoring calculator.

How to use this calculator

  1. Enter water depth, bow roller height above water, expected tidal rise, conditions and the other fields.
  2. The result updates instantly as you type — press Calculate (or Enter) at any time.
  3. Review the breakdown shown under the main result.
  4. Use Copy result or Share to save the answer or send a link with your inputs.

Formula

rode = (depth + bow height + tidal rise) × scope ratio

Worked example

Using the values pre-filled in the calculator above:

  • Water depth = 6 m
  • Bow roller height above water = 1.2 m
  • Expected tidal rise = 2 m
  • Conditions: Calm, all chain (5:1)
  • Boat length = 10 m

the calculator returns:

  • Rode to let out: 46 m
  • In feet: 150.9
  • Total vertical distance: 9.2 m
  • Scope ratio: 5 : 1