Anchor Scope Calculator

Calculate how much rode to deploy at different scope ratios.

Anchoring Conditions

Water Depth: 20 ft

Freeboard / Height Above Water: 4 ft

Rode Type

All Chainmin 5:1Mixedmin 7:1All Ropemin 10:1

Scope Diagram

Showing recommended 7:1 scope · Total height = 20 + 4 = 24 ft

Rode Length Needed

Formula: ratio × (depth + freeboard) = ratio × 24 ft

5:1

Calm / Protected

120 ft

5 × 24 ft

7:1

Standard / OvernightRecommended

168 ft

7 × 24 ft

10:1

Storm / Exposed

240 ft

10 × 24 ft

Exam Tip — Scope Ratios

Scope ratio refers to the ratio of rode length to total depth(depth + freeboard), not just horizontal distance. A 7:1 scope is the standard minimum for overnight anchoring. All-chain rode holds better at lower ratios due to its catenary weight. In storm conditions, deploy 10:1 or more when possible. USCG exam questions typically use 7:1 as the “correct” standard answer.