Free-space path loss calculator

Far-field free-space path loss; no multipath or obstruction.

rf-free-space-loss.napkin / editable

SCENARIO COMPARISON

Compare the numbers.

This source describes an analytical model. Its quantities and checks are the view.

Scenario	wavelengthm	lossDb
	0.124914	80.052
	0.124914	78.1138

All calculated quantities are listed with the inputs. Switch to Source to inspect the equations.

SCENARIOS / CALCULATED VALUESSAME SOURCE

Change an input to see the consequences.

far field distance screen800.55 ✓ passes

BASELINE INPUTS

distance100 mfrequency2400000000 HzlightSpeed299792000 m/s

CALCULATED

wavelength0.12491 m

lossDb80.052

Edits change the baseline source.

THE SOURCE

Edits below update the same model.

# Free-space path loss
# Scope: Far-field free-space path loss; no multipath or obstruction.
# Status: illustrative worked example; engineering review pending.
# Inputs are example values. Checks are editable example requirements, not standards.

distance = 100 m
frequency = 2400000000 Hz
lightSpeed = 299792458 m/s

wavelength := lightSpeed/frequency [m]
lossDb := 20*log10(4*pi*distance/wavelength)

check far field distance screen: distance/wavelength >= 10

scenario alternative: distance = 80 m

Calculated from your source · not saved

Baseline · Baseline

far field distance screen800.55 ✓ passes

alternative · alternative

far field distance screen640.44 ✓ passes

Illustrative first-order example. Checks are editable requirements, not design standards. The broader topic may require additional equations, data, and validation.

Formula and units

This example uses the following equations. Input names and units match the editable source above.

wavelength: wavelength = lightSpeed/frequency [m]
loss db: lossDb = 20*log10(4*pi*distance/wavelength)

Original worked example

These are the baseline values in the downloadable source. Edits above let you test your own values.

Given

distance: 100 m
frequency: 2400000000 Hz
light speed: 299792000 m/s

Calculated

wavelength: 0.124914 m
loss db: 80.052

Assumptions and limits

Far-field free-space path loss; no multipath or obstruction.

The requirement checks use the limits written in this example. Passing a check does not establish that the model covers every load, material behavior, or operating condition in a real design.

Download this .napkin example ↓

Take it further with your agent

Napkin keeps the inputs, equations, checks and assumptions together in one study. Your agent sets it up; you change the numbers.

Try with Claude ↗

codex 'Use Napkin (https://napkin.engineering/mcp, or the local Napkin plugin) to build a study: Free-space path loss. Inputs: frequency; separation distance. Outputs: free-space attenuation; regime assumptions. Model scope: Link and transmission models with declared propagation assumptions. Read napkin_capabilities and the current snapshot. Ask me for the values that matter, label assumptions with units, author .napkin source, validate it and apply it with napkin_source using the current revision, then open the study. Add checks for the limits I supply. Keep unsupported analyses explicit.'

Claude needs the Napkin connector; Codex needs the Napkin plugin. Set up your agent ↗

The broader study

The topic brief below describes the broader scope. The worked example above states the particular calculation it implements.

Inputs: frequency, separation distance
Outputs: free-space attenuation, regime assumptions
Modes: calculate, compare, sweep
Drawing: Link-budget and coverage plots

EXECUTABLE WORKED EXAMPLE · FIRST-ORDER MODEL · CHECK THE SCOPE & ASSUMPTIONS