OceanCalc

Distance to Horizon Calculator — Meters

Find how far the horizon is from your height of eye. Uses the standard nautical formula for horizon distance.

Last updated: March 28, 2026

Author: OceanCalc Editorial Team · Publisher: Albor Digital LLC

Page focus

When you want meter-centric outputs from the Distance to Horizon Calculator, work in the fields above and cross-check against metric charts or soundings.

Distance to Horizon Calculator

Result

Horizon distance (nm)

2.87

Horizon distance (km)

5.31

Formula

Distance (nm) = 1.17 × √(height in feet)

Overview

The Distance to Horizon Calculator helps you perform accurate maritime calculations quickly, using standard nautical relationships and clear inputs.

How to use

Start by filling in the fields for the Distance to Horizon Calculator; the page recalculates as you type so you can iterate through options in one place.

Formula

The relationship behind this tool is: Distance (nm) = 1.17 × √(height in feet)

Distance to horizon (nm) ≈ 1.17 × √(height in feet). In metric: horizon (km) ≈ 3.57 × √(height in meters). Assumes spherical Earth and normal atmospheric refraction.

Your line of sight is tangent to the Earth's surface at the horizon. The greater the height of eye, the farther the tangent point.

Practical use cases

Typical uses for the Distance to Horizon 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 Distance to Horizon 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

  • 6 ft (cockpit): ~2.9 nm (~5.4 km)
  • 30 ft (mast): ~6.4 nm (~11.9 km)
  • 100 ft (bridge): ~11.7 nm (~21.7 km)

Frequently Asked Questions

  • How far can you see at sea?

    From 6 feet (about 1.8 m) above water, the horizon is roughly 2.9 nautical miles (5.4 km) away. From 30 feet it is about 6.4 nm. The formula is distance (nm) ≈ 1.17 × √(height in feet).

  • What is the horizon formula?

    For height of eye in feet: horizon distance in nautical miles ≈ 1.17 × √h. In metric: horizon in km ≈ 3.57 × √(height in meters). This assumes a smooth, spherical Earth and standard refraction.

  • Why does height of eye matter?

    The horizon is the line where the sky meets the sea. The higher your eyes, the farther that line is. On a small boat you see less; from a ship bridge or mast you see much farther.

  • 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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