RF Path Loss Calculator

Tune distance, frequency, antennas, propagation model, and sensitivity to see whether a wireless link closes

animation
networking
rf
propagation
wireless
link-budget
intermediate
A guided RF path-loss and link-budget workbench for comparing free-space, log-distance, indoor-wall, and Hata-style teaching models.
Animation RF Propagation Link Budget

RF Path Loss Calculator

Move distance, frequency, antennas, propagation model, and receiver sensitivity. Watch path loss, received power, link margin, and model warnings update as one connected link-budget story.

91.2 dBEstimated path loss
-57.2 dBmReceived power
20.8 dBFade-adjusted margin
Strong linkLink status

Goal

See how distance and frequency consume link budget before obstacles and fade margin are added.

Try First

Double the distance. Then double the frequency. Watch why each roughly costs 6 dB in free space.

Watch

The chart point, path loss, received power, model warning, and link margin move together.

Why It Matters

A radio link works only when received power stays above sensitivity after realistic margin.

Scenario

Choose a starting link profile.

Model

Choose the propagation teaching model.

Playback

Radio Path

Link Budget

Free-space path loss is the best-case baseline. Real deployments usually need extra margin for clutter, body loss, fading, and antenna orientation.
Received power above target.Expected behavior
1.0 km at 868 MHz.Observed path
Strong link.Working diagnosis

Path Loss vs Distance

The curve uses the selected model. The orange point is the current distance and the dashed line is the maximum allowed loss after fade margin.

Margin: 20.8 dB Target margin: 10 dB

Link Budget Detail

The link has enough fade-adjusted margin for this teaching case.

Model Fitness

The selected model is suitable for this teaching range.

in range

Max Distance

Approximate range where fade-adjusted margin reaches zero.

13.8 km

Sensitivity Pressure

Shows how much receiver threshold and fade margin consume the budget.

-120 dBm target
Beginner Ramp

Path loss is the signal power lost between the transmitter and receiver. Higher path loss means lower received power. The link closes only if received power remains above the receiver threshold with enough fade margin.

Formula Reference
  • FSPL dB = 32.44 + 20log10(distance km) + 20log10(frequency MHz).
  • Received dBm = TX power + antenna gains - cable loss - path loss.
  • Link margin = received power - sensitivity - fade margin.
6 dB Rule

In free space, doubling distance adds about 6 dB loss, and doubling frequency also adds about 6 dB loss. Real clutter, walls, body loss, and antenna mismatch add more.

Model Limits

Free-space is a lower bound for clear line of sight. Log-distance needs a measured or assumed exponent. Hata-style models are empirical and only valid for particular frequency, distance, and antenna-height ranges.

Indoor Warning

Indoor links are dominated by floors, walls, people, metal shelving, and antenna orientation. A wall-loss model is useful for intuition, but not a substitute for a site survey.

Design Margin

Use 6 dB as a bare minimum teaching margin, 10 to 15 dB for many practical plans, and 20 dB or more when high reliability, fading, mobility, or installation variation matters.

Practice 1

Use Free Space at 868 MHz and 1 km. Double distance to 2 km. How close is the loss change to 6 dB?

Practice 2

Switch from 868 MHz to 2400 MHz while keeping distance fixed. What happens to path loss and link margin?

Practice 3

Select Indoor Walls and add walls. Which changes more: the propagation loss, received power, or fade-adjusted margin?

Related Study

Wireless Range CalculatorConnect link budget to practical communication range. Link Budget and AntennasExplore antenna gain, power, and margin in more depth. Fresnel and MultipathSee why line-of-sight clearance affects real links. Radio Duty Cycle CalculatorAfter range closes, check timing and channel-use limits.