Interactive tool
Anchoring scope calculator
Work out how much anchor rode (chain + rope) to pay out for safe holding in any depth and conditions. Choose a scope ratio that matches the weather, your bottom type, and how long you plan to stay.
Enter your water depth, bow height above the waterline, and pick a scope ratio. The tool returns the total rode to deploy plus a chain-length recommendation.
Depth where the anchor will set, measured at high tide.
Height from the water to your bow roller. Adds to effective depth.
Typical day anchorage in fair weather with moderate wind.
Scope is the ratio of rode paid out to the vertical distance from the bow roller to the seabed. More scope means a flatter pull angle on the anchor — and better holding.
3:1 — Lunch hook
Short stop in calm conditions with someone aboard.
5:1 — Standard
Typical day anchorage in fair weather with moderate wind.
7:1 — Overnight
Overnight stays or when wind is expected to freshen.
10:1 — Storm
Heavy weather or unsheltered anchorage. Maximum holding.
About anchoring scope
Scope is what keeps the anchor's shank flat on the bottom so the flukes can dig in. A short, vertical rode lifts the shank and pulls the anchor out — the most common cause of dragging. As a rule of thumb: use more scope in soft bottoms, high wind, or anywhere you can't visually verify the set. Chain near the anchor keeps the pull angle low; nylon rope adds stretch that absorbs wave shock. Always account for tide range — calculate scope at high water, not low. When in doubt, let out more.