Free Space Radio Link Budget Calculator
Calculate ideal free-space received power, entered sensitivity margin and midpoint first-Fresnel radius.
YOUR CALCULATION
Result
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Calculation steps
Work through one step at a time or reveal the complete calculation. The steps use your current inputs.
How to calculate
Use wavelength from the exact vacuum light speed and free-space spreading loss, then add gains/subtract losses on a dB power budget.
FSPL=20log10(4πdistance/wavelength); received dBm=Tx dBm+gains−losses−FSPL
Worked example
At 2.4 GHz and 1 km, ideal free-space loss is about 100.052 dB. The example power/gains/losses give received power about −72.052 dBm and sensitivity margin about 17.948 dB.
Assumptions and input details
Ideal far-field unobstructed free space, not a coverage or regulatory-compliance prediction. The dimensionless spreading factor must be at least one; antenna-aperture far-field limits are otherwise not established. No terrain, fading, interference, rain, polarization or receiver implementation model. Midpoint Fresnel radius is geometric and does not assess actual clearance.
References: ITU: free-space propagation loss
Using this calculator
Can I enter my own problem?
Yes. Replace the example values with your own inputs. The result, calculation steps, tables and applicable diagrams update from those inputs. Blank or invalid values clear the result; example values are never silently substituted for missing inputs.
Are the results exact?
Results use floating-point arithmetic and displayed rounding. Read the formula, assumptions and any stated data precision before interpreting the result.
Is my input uploaded?
The calculation runs in your browser. No account, file upload or external AI service is required. Inputs are not saved between page reloads.
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