First Fresnel Zone Calculator

Calculate first-Fresnel-zone radius and the commonly used 60% clearance target at a selected point on a path.

richie woods

A line-of-sight planning aid for estimating first-Fresnel-zone clearance.

Local calculation: values are processed in your browser and are not transmitted. Optional profiles are stored only in this browser.
Active profile: Manual values
GHz
km
km

Planning output only. Verify assumptions and results against authoritative data, manufacturer information, approved procedures, test evidence and competent engineering or regulatory review before use.

Calculation basis

The first-Fresnel radius at the assessment point uses r₁ = 17.32 × √(d₁d₂ ÷ [f(d₁+d₂)]), where distances are in kilometres, frequency is in GHz and radius is in metres. The tool also reports 60% of that radius as a common planning clearance target.

Limitations and verification

  • Clearance is not the same as a complete propagation analysis.
  • Earth curvature, refraction, terrain data, vegetation, buildings, antenna pattern and diffraction are not modelled.
  • Use surveyed path profiles and representative propagation tools for design assurance.

Version and review status

Formula set: v1.2
Staging review date: 17 August 2026
Status: Staging beta pending user acceptance and cross-browser checks.