Earth Curvature Calculator

Written by Great Medico

Updated September 25, 2026 •2 min read

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When you want a quick earth curvature estimate, the formula matters as much as the final number. For earth curvature, optics can turn a small change in wavelength, aperture, distance, or refractive index into a noticeable change in the result. This calculator applies a specific geometric or wave-optics relationship to the values on the page.

What this calculator does

This calculator estimates how much of a distant line of sight is geometrically hidden by Earth curvature after accounting for observer height. The current headline does not use the target-height field.

How to use it

Start with the fields that drive the current calculation: Target distance, Observer height. Enter values in the units shown beside each field; the page converts supported units before applying the formula. Keep signs and angles consistent with the labels, then read the headline result together with any supporting metrics rather than copying the number without its unit.

How the calculation works

The current calculation finds geometric Earth drop over the entered distance and subtracts observer height to produce a hidden-height estimate. The visible target-height field does not affect the headline hidden-height result in this version.

Example

Using the default example on the page (Target distance = 50 km; Observer height = 2 m), the calculator returns curvature hidden height of 194.204559 m. Change one input at a time and compare the direction of the change with the formula above; that is a quick way to catch a wrong unit, sign, or selected method before you rely on the number.

How to interpret the result

The hidden-height number is geometric obstruction after the observer height is accounted for in the current model. It does not automatically tell you whether a target is visible because the page’s target-height input is not used in the headline calculation. Compare the value cautiously with your target geometry.

Limitations and notes

The current headline ignores target height. The geometry also excludes atmospheric refraction, terrain, Earth ellipsoid details, tides, and line-of-sight obstacles. Use it as a simplified spherical-Earth geometry estimate, not a surveying substitute.