Distance to Horizon Calculator
Calculate how far you can see to the horizon from a given height above sea level for navigation and surveying.
What Is the Distance to the Horizon?
The distance to the horizon is how far you can see before the Earth's curvature blocks your line of sight. A person standing on a beach can see roughly 5 km to the horizon. The taller the observer, the farther the visible distance.
Horizon Distance Formula
$$d = \sqrt{2Rh}$$where \(d\) is the distance to the horizon in meters, \(R\) is Earth's radius (6,371,000 m), and \(h\) is the observer height above sea level in meters. At 2 m height, the horizon is about 5.05 km away.
Practical Applications
Sailors, pilots, and radio engineers use horizon distance to plan line-of-sight communication and navigation. Mounting an antenna higher extends the radio horizon. For surveying and long-range optics, see the Earth Curvature Calculator.
Frequently Asked Questions
What Earth radius does this calculator use?
6,371,000 meters, the mean Earth radius. Results are approximate because Earth is not a perfect sphere.
How far can I see from a 10 m tower?
About 11.3 km. Horizon distance scales with the square root of height, so four times the height only doubles the distance.
Does atmospheric refraction affect the horizon?
Yes. Light bends slightly in the atmosphere, making the horizon appear about 8% farther than the geometric formula predicts.
Can I use feet for height?
Yes. Select feet as the height unit and the calculator converts to meters before applying the formula.
What about two observers at different heights?
Add their individual horizon distances to find the maximum line-of-sight range between them: d_total = √(2Rh₁) + √(2Rh₂).
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