Earth Curve Calculator: How Much Does Earth Curve Over Distance?

The Earth Curve Calculator helps you find out how much the Earth's surface drops over a given distance. Whether you're a photographer checking line of sight, an engineer planning a project, or simply curious about Earth's curvature — this tool gives you instant, accurate results.

What is Earth Curvature?

Earth is not flat — it is a sphere (technically an oblate spheroid). This means its surface curves away from a straight line over distance. The further you look, the more the surface drops below your line of sight. This is why ships appear to sink below the horizon as they sail away.

Earth Curve Formula

The standard formula used to calculate Earth's curvature drop is:

Curve Drop = (Distance²) / (2 × R) Where: Distance = distance in meters R = Earth's radius = 6,371,000 meters

For hidden height (how much of a distant object is hidden below the horizon), the formula accounts for observer height as well.

Hidden Height = Curve Drop − (√(2 × R × h)) Where: h = observer height in meters

How to Use This Calculator

Enter the distance between you and the target object
Select your preferred unit (km, miles, or meters)
Optionally enter your observer height for hidden height result
Click Calculate — results appear instantly

Earth Curvature Over Common Distances

Distance	Curve Drop (approx)
1 km	~0.08 meters
5 km	~1.96 meters
10 km	~7.85 meters
20 km	~31.4 meters
50 km	~196 meters
100 km	~785 meters

Who Uses an Earth Curve Calculator?

1. Photographers & Videographers

Long-distance photographers use Earth curve calculations to determine if a distant mountain or landmark will be visible or hidden behind the horizon from their shooting position.

2. Surveyors & Engineers

Civil engineers and land surveyors must account for Earth's curvature when planning roads, pipelines, bridges, and wireless communication lines over long distances.

3. Amateur Astronomers

Astronomers use curvature calculations to understand how horizon distance affects observations made from sea level versus elevated ground.

4. Aviation & Navigation

Pilots and navigators factor Earth's curvature into flight path planning, especially for long-haul international routes.

5. Flat Earth Debunkers

The Earth curve calculator is a popular tool for testing flat Earth claims by calculating expected object visibility at specific distances — which consistently matches observed reality.

Key Facts About Earth's Curvature

Earth's average radius: 6,371 km
Earth curves approximately 8 inches per mile (the "8 inches per mile squared" rule)
Atmospheric refraction can reduce apparent drop by about 7%
At sea level, the horizon is roughly 4.7 km away for a 1.7m tall person

Conclusion

The Earth Curve Calculator is a simple yet powerful tool for understanding how our planet's spherical shape affects visibility and distance over terrain. Whether for professional use or satisfying curiosity, accurate curvature data is just a click away.