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Simple, accurate, and beautiful Earth Curvature Calculator.

Earth Curvature Calculator screenshot


  1. Light travels in a straight line.
  2. The Earth is a sphere with a radius of 6371 kilometers.

How to use the Calculator?

Calculating the Earth curvature with Horizzn Calculator is a simple three-step process:


Select your measurement preference: 🇺🇸imperial or 🇬🇧metric.


Fill in your EYESIGHT HEIGHT / H in the first input field, that's your eyesight height in relation to sea level. This will return your DISTANCE TO HORIZON / D1.


Fill in your DISTANCE TO TARGET / D in the second input field, that's the distance between you and the target object in the distance. This will return the TARGET HIDDEN HEIGHT / H1 of the distant object/target.

How to calculate Earth curvature?

Assuming Earth is a sphere with a radius of 6371 kilometers we can use the Pythagorean Theorem and accurately calculate the Distance to (the) Horizon.

Then, we can use the Distance to Horizon to calculate the rate of which Earth curves and find the height of the Hidden Target Height of a distant target or an object.

We can manually calculate Earth curvature using these two formulas:

a = √[(r + h)² - r²]

a = Distance to horizon
r = Earth radius
h = Eyesight height
x = √(a² - 2ad + d² + r²) - r 

x = Target hidden height
d = Distance to target


Users of Earth Curvature Calculators all over the world report experiencing mental discomfort due to discrepancies between calculated results and real-life observations.