The Boat Mill

Anchor Rode Length Calculator

Suggest how much rode to let out from depth, bow height, expected tidal rise, and a scope ratio. Assumptions are listed — this is not local harbor advice.

Deck ticket

Sounding or charted depth at the hook.
Bow roller to waterline.
Add rise so scope holds at high water.
Higher scope = flatter pull on the anchor.

How this is calculated

Scope is rode length divided by the vertical distance from bow roller to seabed. This page multiplies that vertical stack by your chosen ratio.

vertical_ft = depth + freeboard + tidal_rise
rode_ft = vertical_ft × scope_ratio

Assumptions: depth and tide are in the same units you enter; holding ground, wind, current, and rode type (all-chain vs rope/chain) are not modeled; 7:1 is a widely cited overnight default, not a guarantee; crowded anchorages may not allow full scope. Not a substitute for local guidance, a charted swinging circle, or seamanship. Volume/KD: unknown.

FAQ

Why add freeboard and tide?

Scope is measured from the bow roller to the seabed, not from the waterline alone. If you set at low water and ignore tide, rising water shrinks your real scope.

All-chain vs rope?

Chain’s weight helps keep a low angle. Mixed rope-and-chain often wants more scope than all-chain in the same weather. This tool does not auto-add for rode type — pick a higher ratio if you use light rope.

Is 7:1 always enough?

No. Poor holding, strong wind, or short rode storage may force different choices. Always set and test the hook; this page only multiplies numbers.

Meters?

Enter every length in meters instead of feet — the ratio math is the same. Keep units consistent.