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.

Height of eye (ft)

Height of the observer's eye above the sea surface; uses the standard coefficient of zero point nine seven minutes of arc per square root foot.

Compute the dip of the visible horizon in minutes of arc as the coefficient zero point nine seven times the square root of height of eye in feet. 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]

Dip (′)

Dip to subtract from sextant altitudes at the standard zero point nine seven coefficient.

• 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 Distance Calculator

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

• 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.

• Lighthouse Geographic Range Calculator

  Compute the geographic range at which a light becomes visible as one point one seven times the sum of the square roots of observer and object heights in feet.