OceanCalc

Geographic Range of a Light Calculator

Estimate combined geographic visible range (nm) from height of eye and light elevation.

Last updated: March 28, 2026

Author: OceanCalc Editorial Team · Publisher: Albor Digital LLC

Geographic Range of a Light Calculator

Result

Geographic range (nm)

14

Formula

d (nm) ≈ 1.17×(√eye + √light), heights in feet

Overview

Use the Geographic Range of a Light Calculator for fast, reliable maritime math—built on standard nautical relationships with straightforward inputs.

How to use

With the Geographic Range of a Light Calculator, type your figures into the inputs above—the output refreshes live, making it easy to sanity-check several cases.

Formula

The relationship behind this tool is: d (nm) ≈ 1.17×(√eye + √light), heights in feet

Optical geographic range sums horizon distances from observer and light. Atmospheric conditions and light power alter actual sighting.

Practical use cases

Typical uses for the Geographic Range of a Light Calculator include passage planning, briefing crew, converting instrument readouts to chart units, and double-checking mental math when fatigue or weather make errors more likely.

Tips for accuracy

  • Confirm that the units you enter match your chart, GPS, or instrument readout before relying on the Geographic Range of a Light Calculator.
  • In rough weather or poor visibility, cross-check important results with a second method or a crew member.
  • Treat simplified models (wave height, radar horizon, etc.) as estimates—real conditions vary with fetch, refraction, and equipment.

Practical examples

  • 9 ft eye, 80 ft light → ~15 nm combined geometric range

Frequently Asked Questions

  • Is this luminous range?

    No—this is geometric horizon range. Nominal range depends on light intensity and visibility.

  • How accurate is this calculator?

    This calculator uses standard maritime formulas and practical approximations where noted. It is suitable for planning and cross-checks; always verify safety-critical decisions with official references and local conditions.

  • Can I use this on mobile?

    Yes. OceanCalc tools are responsive and work on phones and tablets for quick checks on deck or in the cockpit.

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Results are estimates for educational purposes only and should not be used for real navigation decisions.

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