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GEOMETRY TOOL · NO ACCOUNT REQUIRED

Anchor scope calculator.

Calculate anchor rode from water depth, bow height, and scope ratio. The bow is part of the triangle.

Scope equals deployed rode divided by water depth plus bow height, allowing for changing depth and tide. An illustrative 7:1 scope at 10 ft depth and 3 ft bow height needs 91 ft. This does not determine holding or swing clearance.
Slide the drawing sideways to read the full plate.
Measure from the bottom to the bowScope equals deployed rode divided by water depth plus bow height, allowing for changing depth and tide. An illustrative 7:1 scope at 10 ft depth and 3 ft bow height needs 91 ft. This does not determine holding or swing clearance.Reference: BoatUS Foundation — anchoring and mooring

INTERACTIVE CALCULATOR

Adjust the inputs. Estimates update instantly; nothing is uploaded.

YOUR ESTIMATE

Enter measurements to see the calculation.
How it works

Approximate deployed rode = (water depth + vertical height of bow roller above water) × desired scope ratio.

Important limitation

This estimates rode length, not anchor holding power or safe swinging room. Tide, weather, bottom, rode material and boat size change the decision.

IF YOU WANT THE WHOLE STORY

The math is the beginning.

The underwater depth is only part of the triangle. Forget the height of the bow and your rode calculation is optimistic.

Read the companion guide

PUT THE RESULT TO WORK

FX-7: confirm the size before buying the rode

The Fortress FX-7 is one named fluke anchor to evaluate against the manufacturer’s sizing and seabed guidance. Its low mass is useful for handling, but anchor selection still depends on the vessel and conditions. The required rode length follows depth to the bow and scope, not the anchor’s model number.

Read the buying guide →