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 above water (ft)

Height of the observer above the water surface; uses the standard coefficient of one point one seven nautical miles per square root foot.

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. 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]

Horizon distance (NM)

Distance to the horizon at the standard one point one 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 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.

• Horizon Dip Calculator

  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.

• SART Detection Range

  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.