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

Boat count

Required integer. Number of boats competing in the start.

Average boat length (m)

Required number in m. Average overall length of the competing boats.

Scale factor

Optional number. Line lengths provided per average boat length.

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

Recommend a starting line length from the fleet size and average boat length using an adjustable scale factor. Inputs are interpreted exactly in the displayed units and the calculation returns the following fields without presentation rounding.

Recommended line length (m)

Returned number in m. Recommended overall start line length.

• 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.
• Boat count must be at least 2.
• Scale factor must be at least 1.
• Scale factor must be no greater than 6.
• 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.

• Time to Start Line Calculator

  Calculate how many minutes it takes to reach the start line from the remaining distance and current boat speed.

• Beaufort Scale Lookup

  Look up the Beaufort wind force from zero to twelve for a wind speed in knots using standard inclusive upper bounds.

• Gennaker Tack Load

  Estimate the tack line load of a gennaker using tackLoadNewtons = 0.06 * windSpeedMs^2 * sailAreaM2 with a documented gennaker load coefficient.