Use this sailing calculation for planning or education when the vessel, units, reference directions, environmental conditions, and assumptions are explicitly known.

Spring range (m)

Required number in m. Mean tidal range at spring tides.

Neap range (m)

Required number in m. Mean tidal range at neap tides.

The cited overview of Tide supplies background for the terminology and domain context used by this tool.^[1]

Compute the tidal range ratio from rangeRatio = springRangeMeters / neapRangeMeters. Inputs are interpreted exactly in the displayed units and the calculation returns the following fields without presentation rounding.

Range ratio

Returned number. Ratio of spring to neap ranges; larger values indicate stronger tidal asymmetry.

• Vessel design and loading, sea state, wind, current, tide datum, weather, chart accuracy, equipment, crew, and safety margins can make real conditions differ from a simplified result.
• Spring range must be at least 0.
• Neap range must be at least 0.
• Use finite inputs in the displayed units, preserve source measurements and assumptions, and independently verify consequential decisions.

Cross-check current charts, tide and weather services, instrument data, vessel manuals, and applicable navigation rules, and retain a conservative alternative plan.

• Secondary Port Correction

  Compute the secondary port height correction from the signed difference in tidal range and an interpolation proportion taken from almanac tables.

• Anchor Rode Length Calculator

  Compute the anchor rode length needed from water depth, freeboard, and scope ratio.

• Anchor Scope Ratio Calculator

  Compute the scope ratio from the deployed rode length and the total height to the bow chock.