Fresnel Zone Calculator

Information and Tips

Fresnel Zone Calculator

The Fresnel Zone Calculator helps estimate the radius of the first Fresnel zone for wireless links, radio bridges and point-to-point antenna installations. Maintaining sufficient clearance around the direct line of sight is important for stable signal quality, especially over longer distances.

Calculate the First Fresnel Zone





 
For practical radio links, at least 60% of the first Fresnel zone should usually be clear of obstacles. Full clearance is preferred where possible.

Formula

r = sqrt((n × λ × d1 × d2) / (d1 + d2))

Where r is the Fresnel zone radius, n is the Fresnel zone number, λ is the wavelength, d1 is the distance from antenna A to the obstacle, and d2 is the distance from the obstacle to antenna B. This calculator uses n = 1, which means the first Fresnel zone.

Why Fresnel Zone Clearance Matters

A radio link may have a visible line of sight and still perform poorly if the first Fresnel zone is blocked by trees, roofs, terrain, metal structures or other obstacles. Such obstruction can cause signal attenuation, reflections, multipath propagation and unstable throughput.

This is especially important for outdoor Wi-Fi links, 5 GHz and 6 GHz radio bridges, point-to-point installations, industrial networks and long-distance antenna systems.

Typical Examples

Frequency Distance Approx. first Fresnel zone radius in the middle 60% clearance
2.4 GHz 1 km 5.6 m 3.4 m
5.8 GHz 1 km 3.6 m 2.2 m
5.8 GHz 5 km 8.0 m 4.8 m
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