Use this sailing calculation as a planning or educational cross-check for navigation, wind and current, rig loads, stability, anchoring, tides, visibility, performance, or recovery under explicitly stated conditions.

Nominal range (NM)

Charted luminous range of the light in clear conditions.

Visibility (NM)

Prevailing meteorological visibility; ranges above ten nautical miles can increase the luminous range.

Correct a navigation light's nominal range for prevailing meteorological visibility using Allard's inverse-square and atmospheric-transmission relation. Nominal range is defined at ten nautical miles of visibility. The tool evaluates the supplied inputs together and returns the named outputs below; it does not infer omitted operating conditions or change the units shown.^[1]

Corrected range (NM)

Expected range at which the light becomes visible in the given visibility.

• Actual conditions change with vessel design and loading, sea state, wind, current, tide datum, weather, chart accuracy, equipment, crew, regulations, and safety margins. Simplified formulas do not replace seamanship, approved stability data, or current navigation information.
• Use finite inputs in the displayed units and preserve more precision than the final presentation requires. Independently verify safety-critical, financial, compliance, or production decisions.

Cross-check official charts, tide and weather services, instrument data, vessel manuals, and collision regulations; maintain conservative margins and a safe alternative plan.

• Horizon Range Calculator

  Compute the distance to the visible horizon in nautical miles as one point one seven times the square root of the observer height in feet.

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  Estimate the radar detection range of a search and rescue radar transponder as one point one seven times the sum of the square roots of the SART mounting height and the responding antenna height in feet, capped at forty nautical miles.

• Sound Signal Range

  Estimate the audible range of a vessel sound signal from its whistle output level in decibels using two nautical miles above one hundred and thirty decibels, one nautical mile above one hundred and ten, and half a nautical mile otherwise.