Friis Free-Space Path Loss (FSPL = 20·log₁₀(d) + 20·log₁₀(f) + 32.44 dB) Calculator

Compute Free-Space Path Loss (dB) and wavelength λ across Wi-Fi, LoRa, Cellular, and SatCom bands.

Free-Space Path Loss (FSPL)
114.02 dB
Carrier Wavelength (λ = c / f) 12.49 cm
FSPL at 2× Distance (+6.02 dB) 120.04 dB
Linear Attenuation Ratio (10^(FSPL/10)) 252,558,792,265.21 ratio
Inputs
⚡ Scenarios:
km
Line-of-sight distance between transmitter and receiver (km).
MHz
Carrier radio frequency in MHz (e.g., 915 MHz LoRa, 2400 MHz Wi-Fi, 5800 MHz).
Results & Graph
Free-Space Path Loss (FSPL)
114.02 dB
Carrier Wavelength (λ = c / f)
12.49 cm
FSPL at 2× Distance (+6.02 dB)
120.04 dB
Linear Attenuation Ratio (10^(FSPL/10))
252,558,792,265.21 ratio

Free-Space Path Loss (FSPL)

Graph 1 • Free-Space Path Loss (FSPL) • Domain Architecture & Live Telemetry Maps Link Distance Km, Carrier Frequency Mhz through Free-Space Path Loss (FSPL) Formula.
Source / Tx Target / Rx Free-Space Path Loss (FSPL) Propagation Path Free-Space Path Loss (FSPL 114.02 dB Carrier Wavelength (λ = c : 12.49 cm FSPL at 2× Distance (+6.02: 120.04 dB
Graph 2 • Free-Space Path Loss (FSPL) Across Link Distance Km Sweep (40% → 160%) Evaluates FSPL (dB) = 20·log₁₀(Distance_km) + 20·log₁₀(Frequency_MHz) + 32.44; λ across 7 operating points (current input highlighted).
0 dB 64.96 dB 129.9 dB 106.1 2km 109.6 3km 112.1 4km 114.0 5km 115.6 6km 117.0 7km 118.1 8km
Graph 3 • Joint Sensitivity: Link Distance Km × Carrier Frequency Mhz Compares Free-Space Path Loss (FSPL) when Carrier Frequency Mhz is shifted +25% (solid) vs. −25% (dashed).
0 dB 65.03 dB 130.1 dB --- Carrier Frequency Mhz @ 75% 112.9 -30% 114.5 -15% 116.0 +0% 117.2 +15% 118.2 +30%
Summary: At 5 km and 2400 MHz (wavelength λ = 12.49 cm), Free-Space Path Loss is 114.02 dB (doubling distance or frequency adds +6.02 dB).
Summary: At 5 km and 2400 MHz (wavelength λ = 12.49 cm), Free-Space Path Loss is 114.02 dB (doubling distance or frequency adds +6.02 dB).
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Formula & Mathematical Methodology: Free-Space Path Loss (FSPL) Formula

FSPL (dB) = 20·log₁₀(Distancekm) + 20·log₁₀(FrequencyMHz) + 32.44
λ = c / f
FSPL (dB) = 20·log₁₀(Distance_km) + 20·log₁₀(Frequency_MHz) + 32.44; λ = c / f
  • linkDistanceKm: Link Distance Km (km)
  • carrierFrequencyMhz: Carrier Frequency Mhz (MHz)

Rounding: Engineering outputs round to 2–3 decimal places; discrete material bag/unit counts round up via ceiling.

Worked Example: Engineering Scenario: Free-Space Path Loss (FSPL)

Compute Free-Space Path Loss (dB) and wavelength λ across Wi-Fi, LoRa, Cellular, and SatCom bands.

  1. Enter your system dimensions, electrical/RF ratings, or environmental conditions.
  2. Evaluate the governing equation: FSPL (dB) = 20·log₁₀(Distance_km) + 20·log₁₀(Frequency_MHz) + 32.44; λ = c / f.
  3. Inspect the primary design output, supporting allowances, and 3 SVG schematics.
Result: Computes Free-Space Path Loss (FSPL) via FSPL (dB) = 20·log₁₀(Distance_km) + 20·log₁₀(Frequency_MHz) + 32.44; λ = c / f.

Frequently Asked Questions

How does the Friis Free-Space Path Loss (FSPL = 20·log₁₀(d) + 20·log₁₀(f) + 32.44 dB) Calculator calculate results?

It evaluates FSPL (dB) = 20·log₁₀(Distance_km) + 20·log₁₀(Frequency_MHz) + 32.44; λ = c / f directly in your browser and updates three custom SVG visualizations in real time.

Can I use Goal Seek to solve backwards for a required dimension or rating?

Yes. Click "🎯 Goal Seek" in the results toolbar to solve backwards for any numeric input parameter.

Does this engineering calculator work offline?

Yes. All calculations run 100% locally in your browser and work offline via the CalculatorGraph PWA.

Science & Engineering · RF, Telecom & Antenna Engineering

Friis Free-Space Path Loss (FSPL = 20·log₁₀(d) + 20·log₁₀(f) + 32.44 dB) Calculator: inputs, method, and how to read the result

Compute Free-Space Path Loss (dB) and wavelength λ across Wi-Fi, LoRa, Cellular, and SatCom bands.

Choose inputs for the case you are checking

The defaults are illustrative. Replace them with values for your case and keep the units shown beside each field.

  • Link Distance Km: Line-of-sight distance between transmitter and receiver (km).
  • Carrier Frequency Mhz: Carrier radio frequency in MHz (e.g., 915 MHz LoRa, 2400 MHz Wi-Fi, 5800 MHz).

What the calculation includes

With the default values shown, Free-Space Path Loss (FSPL) is 114.02 dB. The calculation follows Free-Space Path Loss (FSPL) Formula; the formula and variable definitions above show how the inputs combine.

One-input check: With the other defaults held constant, changing Link Distance Km from 5 km to 6 km changes Free-Space Path Loss (FSPL) from 114.02 dB to 115.61 dB. This is a comparison inside the calculator's stated model, not a prediction.

Where to use caution

  • Uses standard NREL, IEEE, ASHRAE, and IRC design equations.
  • Verify final structural, electrical, and mechanical specifications against local building codes.

Scope: Global Engineering & Building Code Standard Check the assumptions and limitations against your situation before relying on the estimate.

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