Fresnel Zone Calculator

Calculate Fresnel zone radii at an obstruction point and determine required clearance for LOS links.

What is a Fresnel Zone?

RF signals don't travel in a laser-thin beam — they spread out in an invisible elliptical bubble between transmitter and receiver, like a stretched football. This bubble is the Fresnel zone. Any object that pokes into this zone — a tree, a hill, a building — causes the signal to weaken, even if it doesn't physically block the direct line of sight.

Why it matters: Wireless internet providers check Fresnel zones before installing point-to-point links to ensure trees won't grow into the zone and degrade your signal over time.

Link Parameters
Frequency, path distance, and obstruction location.
MHz

Higher frequencies have smaller Fresnel zones. 2.4 GHz WiFi = 2400 MHz, 5 GHz = 5000 MHz

km

The straight-line distance from your transmitter to your receiver

km

Where the obstacle is along the path — must be between TX and RX. The zone is largest near the midpoint

d1 = 4 km from TX · d2 = 6.00 km to RX · λ = 12.49 cm

Fresnel Zone Radii
Zone radii at the obstruction point (4 km from TX).
obstacleTXRXF1F2F3

Required clearance: 10.39 m

60% of first Fresnel zone radius — minimum obstacle clearance for no significant diffraction loss

ZoneRadius (m)Radius (ft)vs F1
F117.3156.8—
F224.4980.3×1.41
F329.9998.4×1.73
F434.63113.6×2.00
F538.72127.0×2.24
60% clearance10.3934.10.60×

Obstacles within the first Fresnel zone cause significant signal degradation. 60% clearance of F1 maintains free-space propagation conditions. Higher-order zones partially cancel each other.