United States calculator
Estimate geometric drop and hidden height over distance
Use U.S. miles/feet or enter a custom refraction factor to compare straight-line sight with a spherical Earth model.
curved Earth sight line
Project inputs
Earth Curvature Calculator results
How this Earth Curvature Calculator works
Drop is computed from spherical geometry rather than the rough eight-inches-per-mile-squared shortcut. The optional effective-radius factor represents atmospheric refraction scenarios.
Important: Refraction varies with weather; this is not a surveying certification.
What assumptions should I verify?
Check every entered quantity, unit, rate and rule against the current U.S. source that applies to your project. The calculator does not silently substitute worldwide conventions.
Is information sent anywhere?
No. Calculations run locally in the browser and the module contains no analytics, remote requests or stored personal data.