Satellite Internet Coverage Radius Calculator

This calculator estimates the ground coverage radius of a satellite from orbital altitude and a chosen minimum elevation angle. It uses spherical Earth geometry to approximate the footprint within which the satellite remains at or above that elevation threshold.

The output includes ground radius, footprint diameter, and surface area, which can help with first-pass visibility studies and constellation planning. The geometry is intentionally idealized: terrain, atmospheric effects, antenna patterns, regulatory masks, beam steering, link budget, and the operator’s actual service beam can all reduce usable coverage compared with the geometric footprint.

Orbit and visibility inputs

Satellite altitude

Minimum elevation angle

Earth radius used

Result

—

Estimated ground coverage radius

Footprint diameter—

Approx. surface area—

Central angle—

Horizon radius at 0° elevation—

How to use

1. Enter orbital altitude

Use the satellite altitude above Earth’s surface, not distance from the ground terminal to the satellite.

2. Set minimum elevation

Enter the lowest elevation angle at which you consider the satellite usable. Raising this threshold reduces the geometric footprint.

3. Check Earth radius

The default 6,371 km is a common mean-radius approximation. Change it only if your analysis deliberately uses another spherical radius.

4. Review the footprint

Use the radius and diameter for distance planning and the surface-area result for an approximate spherical-cap footprint.

5. Apply practical constraints separately

Compare the geometric result with beam shape, antenna performance, terrain, link budget, and service-area restrictions before using it operationally.

Formula

The geometric footprint is based on satellite altitude, Earth radius, and the minimum elevation angle required at the ground terminal.

ψ = arccos[(R ÷ (R + h)) × cos(e)] − e Ground radius = R × ψ Footprint area = 2πR² × (1 − cos(ψ))

R is Earth radius in kilometers, h is satellite altitude above the surface in kilometers, e is minimum elevation angle in radians, and ψ is the Earth-centered coverage angle in radians. Ground radius is the great-circle surface distance from the sub-satellite point to the elevation-angle boundary.

The model treats Earth as a sphere and describes geometric visibility only. It does not establish whether the radio link has sufficient signal strength or whether an operator serves the entire footprint.

What the result means

Use the result as a planning estimate based on the values entered. Compare it with measured performance or system-specific engineering limits before making a deployment decision.

Changing any input updates the result automatically; Reset restores the example defaults shown on this page.

Example calculation

Given: altitude 550 km, minimum elevation 25°, and Earth radius 6371 km.

Calculation: Convert 25° to radians, then ψ = arccos[(6371 ÷ 6921) × cos(25°)] − 25° = 8.459°. Ground radius = 6371 × 0.147629 = 940.5 km. Surface area = 2π × 6371² × (1 − cos ψ) ≈ 2774093 km².

Result: The idealized geometric footprint has a ground radius of about 940.5 km.

FAQ

Why does a higher minimum elevation angle reduce coverage?

A higher elevation requirement removes low-angle lines of sight near the geometric horizon. That shrinks the ground area from which the satellite meets the chosen visibility threshold.

Is this the same as the satellite beam radius?

No. A service beam can be smaller, shaped, steered, or limited by power and regulatory constraints. This calculator estimates only the geometric visibility footprint for the elevation angle.

Does the calculator account for Earth being an oblate spheroid?

No. It uses the Earth radius entered as a sphere. That is appropriate for a first-pass estimate but not for precise geodetic or mission analysis.

Can I use geostationary altitude?

Yes, as long as the altitude is entered in kilometers above Earth’s surface and remains within the input range. The geometry works across a broad range of orbital altitudes.

Why can usable coverage be much smaller than this result?

Link budget, atmospheric attenuation, antenna gain, terrain blockage, interference, beam design, gateway availability, and service restrictions can all reduce practical coverage.

Related tools