Fresnel Zone Radius Calculator

About this calculator

The first Fresnel zone is an ellipsoid-shaped region around the straight line-of-sight path between two radio antennas; even if that direct line is unobstructed, objects intruding into this zone (trees, buildings, terrain) can still cause diffraction losses that weaken the signal. Its radius at any point along the link — widest at the midpoint — is calculated as r = 17.3 × √(d1·d2 / (f·D)) meters, where d1 and d2 are the distances (km) from each end to that point, D is total link distance, and f is frequency in GHz.

Wireless link designers apply the standard 60% clearance rule: as long as at least 60% of the first Fresnel zone radius stays clear of obstructions, diffraction loss is negligible, which is why this calculator reports both the full first-zone radius and the 60% clearance figure. This calculation is fundamental to planning point-to-point microwave backhaul, fixed wireless access, and long-range Wi-Fi links, since lower frequencies produce a larger, more obstruction-sensitive Fresnel zone than higher frequencies over the same distance.