Anchor Swing Circle Calculator
Estimate swing radius and safe clearance before you set the hook.
⚓Anchoring Presets
⚙Scope And Geometry Inputs
📊Reference Scope Table
| Condition | Typical Scope | Use Case | Watch Item |
|---|---|---|---|
| Short stop | 3:1 | Day anchoring in calm water | Fast wind shift margin is low |
| Normal overnight | 5:1 | Sheltered anchorage | Monitor tide rise in radius |
| Windy or chop | 7:1 | Open bay exposure | Large circle requires spacing |
| Conservative hold | 10:1 | Heavy weather planning | Very wide swing footprint |
An anchor swing circle is the space boat or ship moves around its anchor because of wind, flow or tide. Its radius depends on the length of the anchor cable and the water depth. Wind changes and the ship turns to face the wind, with the anchor as center that keeps it in a set area
Although the anchor holds, the ship stays in a small and safe zone. You call it also anchor turning circle, turning radius or drag circle, although that last one is a bit diffrent. At anchoring you need enough room, so that it does not hit shallows or nearby ships.
How to Find Your Anchor Swing Circle
The Anchor Swing Circle Calculator is useful to sailors. It estimates the zone around the anchored boat, to avoid collisions with objects during swinging because of wind or flow. Draw a little circle on the chart around the anchor spot, using the ship length and cable length.
Normal proportion is at least 5:1, so five times the water depth, for good anchoring. To estimate the swinging circle, multiply the rode length by the proportion. For instance in 10 feet depth with 5:1, the boat will swing around 50 feet radius plus its length.
Ideally, do not anchor more closely than 50 feet plus boat length to other ships.
The calculations can become complex. At ships with whole chain, the diameter matches chain length plus ship length and depth on the chart. You take shackles multiplied by 27.5 meters plus distance of GPS antenna to front.
Only chain stays almost vertical from the ship chain to bottom, which shortens the circle, if no strong tide or wind pulls it.
Fixed anchor alarms help. For instance with 50 feet chain, 125 feet as alarm point give too many false signals. Increase to 145 feet commonly give peace.
Choose two horizon landmarks and check their positions to control drifting. Never bind the anchor to the backofthe boat.
