Distance to the horizon
Calculate how far you can see from a given height, such as from a beach, a building, a hill or a plane, with and without atmospheric refraction, the maximum distance to see a tall object and how much of it is hidden by the curvature of the Earth.
How to useHow far can you see
See a distant object
Mean Earth radius of 6,371 km. With refraction, it uses an effective radius of about 7,430 km (factor 3.86). Fog and pollution greatly reduce real visibility.
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Distance to the horizon: what it is for
Find out how far you can see from any height: standing on the beach, from the top of a building, a hill or a plane. The tool shows the distance to the horizon, with and without atmospheric refraction (factors of 3.86 and 3.57 times the square root of the height), how far the horizon dips below eye level and the visible area. It also calculates the maximum distance to see a tall object and how much of it is hidden by the curvature of the Earth.
The calculations run in your browser, without sending anything to a server.
How to use
- Enter the height of your eyes.
- Choose with or without refraction.
- Enter the height and distance of an object to see what is visible.
When to use it
- Curiosity on trips and at the beach.
- Navigation and watching the sea.
- Physics and geography lessons.
Frequently asked questions
How far away is the horizon?
The geometric distance is d = √(2 × R × h), where R is the Earth's radius and h the height of your eyes. With h in meters and d in kilometers, that is about 3.57 × √h. A person standing on the beach, with eyes at 1.7 m, sees the horizon about 4.7 km away.
How does refraction change the result?
The atmosphere bends light slightly downward, which lets you see a little beyond the geometric horizon. In normal conditions the factor goes from 3.57 to about 3.86, a gain of around 8% in distance. During temperature inversions, the difference can be much larger.
How far away can I see a building or a mountain?
Add the horizon distance of the observer and that of the top of the object. An observer 2 m high can see the top of a 100 m building up to about 44 km away, with refraction, if the air is clear. Farther than that, the whole building is below the horizon.
Is it really free?
Yes, 100% free. No sign-up, no subscription and no usage limits. All Tools123 tools are free and run right in your browser.