Educational rode geometry: compute scope from rode length and effective depth (depth + optional freeboard), and estimate horizontal distance to the anchor when the rode is longer than depth. Complements the rode-length sizing tool. No OEM chain lb/ft tables.
Reach for the anchor scope & horizontal calculator when a planning number depends on measurements you already have on the boat or trailer. Enter rode length (ft), depth (ft), and freeboard / bow height (ft, optional).
Educational rode geometry: compute scope from rode length and effective depth (depth + optional freeboard), and estimate horizontal distance to the anchor when the rode is longer than depth.
Scope equals rode length divided by effective depth (water depth plus optional freeboard). When rode is longer than effective depth, horizontal reach is approximated as the right triangle √(rode² − depth_eff²). Straight-line geometry — not a catenary or chain-weight model.
scope = rode ÷ (depth + freeboard)
horizontal ≈ √(rode² − depth_eff²) when rode > depth_eff
Complements anchor rode length (sizes rode from desired scope). No OEM chain tables.
Start with the calculator’s default entries: Rode length (ft) = 100; Depth (ft) = 15; Freeboard / bow height (ft, optional) = 4.
With those entries the calculator returns:
5.26:1 scope
horizontal 98.2 ft · depth_eff 19.0 ft
depth_eff = 15 + 4 = 19.00 ft
scope = 100 ÷ 19.00 = 5.263:1
horizontal ≈ √(100² − 19²) = 98.18 ft
Formula used: scope = rode ÷ (depth + freeboard) horizontal ≈ √(rode² − depth_eff²) when rode > depth_eff
One input at a time. Raise Rode length (ft) from 100 to 150 and leave everything else alone. The result becomes:
7.89:1 scope
horizontal 148.8 ft · depth_eff 19.0 ft
scope = 150 ÷ 19.00 = 7.895:1
horizontal ≈ √(150² − 19²) = 148.79 ft
This anchor scope & horizontal page models the arithmetic shown in the formula box only.
No. Catenary needs chain weight and tension inputs. This page uses straight-line hypotenuse geometry as a simple planning approximation.
Many planners prefer higher scope in open water. This tool reports the ratio; you choose the policy.
Use the anchor rode length calculator instead.