Radar Horizon Calculator
Updated recently with improved calculation accuracy and expanded examples.
Approximate radar line-of-sight horizon in nautical miles from antenna height.
Last updated: August 28, 2026
Author: OceanCalc Editorial Team · Publisher: Albor Digital LLC
Radar Horizon Calculator
Result
Radar horizon (nm)
7.7
Formula
Approximate radar horizon: d (nm) ≈ 1.23 × √(h ÷ 0.3048), where h is antenna height in meters.Model note: This calculator uses the standard 4/3-Earth-radius approximation for radar horizon; actual detection range can vary with atmospheric refraction, antenna height, terrain, and target height.
What is the Radar Horizon Calculator?
Approximate radar line-of-sight horizon in nautical miles from antenna height.
This is an approximate radar-horizon calculation using a standard 4/3-Earth-radius atmospheric-refraction model; actual radar range can vary with atmospheric conditions, antenna height, and target characteristics.
nautical chart
A nautical chart is a map for navigation showing depths, aids, hazards, and often magnetic variation; distances are read with the latitude scale for nautical miles.
Related Maritime Calculators
Overview
A nautical chart is a map for navigation showing depths, aids, hazards, and often magnetic variation; distances are read with the latitude scale for nautical miles. A Radar Horizon Calculator is used in maritime navigation to perform precise calculations based on established nautical formulas. This tool allows you to apply your inputs to the stated nautical relationships using accurate and standardized methods.
Key takeaways
- Radar Horizon Calculator — A nautical chart is a map for navigation showing depths, aids, hazards, and often magnetic variation; distances are read with the latitude scale for nautical miles.
- Formula — Empirical radar horizon approximation; target detectability also depends on power, sea clutter, and target height.
- How to use — Fill the inputs for the Radar Horizon Calculator; the tool recalculates live as you edit.
How to use
Fill the inputs for the Radar Horizon Calculator; the tool recalculates live as you edit.
Formula
Core relationship: Approximate radar horizon: d (nm) ≈ 1.23 × √(h / 0.3048), where h is antenna height in meters.
Empirical radar horizon approximation; target detectability also depends on power, sea clutter, and target height.
This is an approximate radar-horizon calculation using a standard 4/3-Earth-radius atmospheric-refraction model; actual radar range can vary with atmospheric conditions, antenna height, and target characteristics.
Practical use cases
Radar Horizon Calculator: passage planning, crew briefings, instrument-to-chart unit checks, and verifying mental math when tired or in rough weather.
Tips for accuracy
- Match input units to your chart, GPS, or instrument before trusting the Radar Horizon Calculator.
- Cross-check important outputs with a second method or crew when visibility or motion is poor.
- Treat simplified models (waves, radar horizon, etc.) as estimates; real conditions vary.
Practical examples
- 12 m scanner → ~7.7 nm to the sea surface.
Frequently Asked Questions
How accurate is this calculator?
It uses standard maritime formulas and noted approximations. Use it for planning and checks; confirm safety-critical decisions with official sources.
Can I use this on mobile?
Yes. Layouts are responsive for phones and tablets on deck or in the cockpit.
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These calculations are based on standard maritime navigation formulas used in seamanship, chart navigation, and marine route planning.
Results are estimates for educational purposes only and should not be used for real navigation decisions.