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Anchor Scope Calculator

Anchor Scope Calculator

Maritime Calculators

Calculate safe anchor rope length, bow freeboard adjustments, and GPS swing circle radius

Measurement System & Units

Always calculate using expected high tide water level.

Vertical height from water line to anchor roller / cleat.

Ratio of anchor line let out vs total elevation.

Calculated Mooring Recommendations
Required Chain (No. of Shackles)
1.9shackles(168.00 ft)

Standard marine shot: 1 shackle = 90 feet (15 fathoms).

GPS Swing Circle Radius (Horizontal)
166.3ft

Your vessel will swing in a horizontal diameter of approx. 333 ft around the anchor point.

IMO & IACS Commercial Anchorage Standards
  • Factor in High Tide & Under-Keel Clearance: When anchoring high-draft bulkers or VLCCs in tidal roadsteads, always calculate total chain required based on maximum predicted high tide while actively monitoring low-tide Under-Keel Clearance (UKC).
  • Ballast Condition & Hawsepipe Freeboard: On unladen commercial vessels in ballast, deck hawsepipe freeboard stands high above the waterline. Ignoring this elevation results in too short a chain angle and immediate risk of dragging in current.
  • Check GPS Swing Circle in Roads: Verify your calculated horizontal swing diameter stays well clear of adjacent anchored tonnage, shipping fairway lanes, and shoal boundaries during tidal reversals.
Chain Shots & Windlass Braking Limits

Engineering physics of commercial stud-link anchor chain:

  • Standard Chain Shots: Commercial anchor chain is forged in uniform 15-fathom shots (90 ft / 27.43 m) joined by detachable Kenter shackles, painted and marked with stainless wire bindings so the deck officer can report precise shots lowered over the windlass gypsy.
  • Holding Power & Windlass Limits: Under IACS rules, ship anchoring equipment is designed to hold a vessel only in moderate weather and tides. In Force 7+ gales, heavy chain catenary straightens; main propulsion must be placed on standby to relieve tension before brake slippage or hawser damage occurs!
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