Anchor Scope Calculator
Scope is the ratio of anchor line, called rode, to the distance from the bow down to the seabed. This works out the rode length for the ratio you pick, and shows the sum.
- Free
- Works offline after your first visit
- Saves on this device
- No sign-up
- Updated
How it works
Add the water depth to the height of the bow above the water. That is the distance from the bow down to the seabed.
Multiply that distance by the scope ratio you choose. A higher ratio gives more rode and a flatter pull on the anchor. Many cruising sources give a ratio of about 5 to 1 for normal conditions.
Worked example
In 12 ft of water, with the bow 4 ft above it, a scope of 5 to 1 calls for 80 ft of rode.
Questions
What scope should I use?
That depends on the wind, the seabed and the boat. This shows the sum for the ratio you enter, and the choice is yours to make.
Which depth should I use?
Use the deepest level you expect, which is usually high tide, and add whatever margin you want. The water is shallower at low tide.
Why not let out as much as possible?
More rode can run the anchor flatter, but it also needs room to swing. Leave space for the boat to move around the anchor.
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