Work out anchor chain length instantly with clear inputs, formula shown and shareable results.
Scope is measured from the bow roller, not the waterline, so bow height must be added to the depth. Five to one is the normal minimum for chain, seven for strong wind and ten in a storm; rope needs 50% more because it lacks the catenary weight that keeps the pull horizontal.
Anchor scope
rode length = (depth + bow height) x scope ratio; chain 5:1 normal, rope 7.5:1
Chain's weight forms a catenary curve that keeps the pull at the anchor shank horizontal. Rope floats up under load, lifting the shank and reducing holding power.
Yes, always calculate on high water depth. Anchoring on a rising tide with minimum scope is a classic way to drag at 3 am.