Atmospheric Attenuation Calculator

Enter propagation and weather inputs

Frequency (GHz)

Horizontal path length (km)

Elevation angle (degrees)

Temperature (°C)

Pressure (hPa)

Relative humidity (%)

Rain rate (mm/h)

Fog liquid water density (g/m³)

Fade margin (dB)

Reset

The model uses engineering approximations for planning, screening, and comparative studies. For compliance work, validate results with your adopted propagation standard.

Example data table

Scenario	Frequency	Path	Humidity	Rain	Fog	Elevation	Total attenuation
Microwave backhaul	15 GHz	5 km	70%	25 mm/h	0.20 g/m³	10°	8.61 dB
Heavy weather link	30 GHz	8 km	85%	50 mm/h	0.40 g/m³	5°	35.30 dB
High-frequency path	60 GHz	2 km	60%	10 mm/h	0.10 g/m³	20°	51.88 dB

Formula used

Saturation vapor pressure: e_s = 6.112 × exp[(17.67 × T) / (T + 243.5)]
Water vapor pressure: e = RH × e_s / 100
Absolute humidity: ρ_v = 216.7 × e / (T + 273.15)
Temperature ratio: θ = (T + 273.15) / 288.15
Dry-air attenuation: γ_d = 0.00012 × f² × (P / 1013.25) / θ² × oxygen boost
Water-vapor attenuation: γ_w = 0.000015 × f² × (ρ_v / 7.5) / θ² × vapor boost
Slant path: L_s = L / max[sin(ε), 0.1]
Rain attenuation: γ_r = k × R^α, where k and α vary with frequency
Fog attenuation: γ_f = 0.08 × M × (f / 10)² / [1 + (f / 100)²]
Total physical attenuation: A = A_gas + A_rain + A_fog
Design attenuation: A_design = A + fade margin

How to use this calculator

Enter the operating frequency in gigahertz for the path you are studying.
Add the horizontal path length and the link elevation angle.
Provide local weather values for temperature, pressure, and humidity.
Enter rain rate and fog liquid water density when those effects matter.
Set a fade margin to reflect your design allowance or reliability target.
Click the calculate button to display losses above the form.
Review gaseous, rain, and fog components before comparing the total.
Use the CSV or PDF buttons to save the result summary.

Frequently asked questions

1) What does atmospheric attenuation mean?

It is the signal loss caused by gases, water vapor, rain, fog, and slant-path geometry while a wave travels through the atmosphere.

2) Why is elevation angle included?

Lower elevation angles increase the effective path through air and weather layers, so the same horizontal distance can produce noticeably higher attenuation.

3) Does humidity always matter?

Humidity matters more as frequency increases, especially near water-vapor absorption regions. At lower frequencies, its contribution is often smaller than rain loss.

4) Is rain loss calculated separately?

Yes. The calculator estimates specific rain attenuation from frequency and rain rate, then applies an effective weather path to produce total rain loss.

5) What is fog liquid water density?

It represents the mass of suspended liquid water per cubic meter of air. Dense fog has a larger value and usually causes stronger attenuation.

6) Should I trust the result for compliance work?

Use it for screening, planning, and comparisons. Formal compliance or contractual designs should still be checked against your required propagation standard.

7) What does design attenuation show?

It adds your chosen fade margin to the calculated physical loss, giving a more conservative figure for engineering decisions and link budgeting.

8) Can I export the results?

Yes. After calculating, use the CSV button for spreadsheet work or the PDF button for a quick report snapshot.