RF Link Budget Calculator

Link parameters — transmitter → receiver

Frequency (MHz)

MHz

(3.5 GHz typical for 5G)

Distance (km)

TX power (dBm)

TX antenna gain (dBi)

RX antenna gain (dBi)

LNA gain / preamp (dB)

TX cable loss (dB)

RX cable loss (dB)

Rain / atmos loss (dB)

Polarization mismatch (dB)

Misc. losses (dB)

Noise figure (dB)

Bandwidth (kHz)

kHz

Required SNR (dB)

Fade margin target (dB)

Free-space path loss (ITU) · Rx power includes all gains/losses · Sensitivity = -174dBm/Hz + NF + 10log(BW) + SNR

Real‑time link budget & margin

RX POWER @ LNA OUTPUT -74.3 dBm

LINK MARGIN 11.6 dB

Margin vs target: -3.4 dB below target

FS Path Loss 129.1 dB

Rx Sensitivity -98.2 dBm

EIRP 49.5 dBm

Noise Power -110.2 dBm

All parameters update live — click ⟲ reset to 5G example

Link budget breakdown

TX power
33.0 dBm

- TX cable
1.5 dB

+ TX ant
18.0 dBi

- FSPL
129.1 dB

- misc/rain
1.3 dB

+ RX ant
21.0 dBi

- RX cable
1.2 dB

+ LNA
2.0 dB

= Rx power
-74.3 dBm

Created by

Narendra Kumar

Last Updated: 13-02-2026

What Is Link Budget?

A link budget is a systematic calculation of all gains and losses that a communication signal experiences from the transmitter to the receiver, used to determine the received signal power and ensure reliable communication with sufficient signal-to-noise ratio (SNR).

It accounts for transmitter power, antenna gains, cable losses, free-space path loss, atmospheric attenuation, and receiver characteristics. Engineers use the link budget to verify that the received signal exceeds the receiver sensitivity by an adequate link margin, ensuring stable performance under real-world conditions such as fading and interference.

Basic Link Budget Equation

The simplified equation in logarithmic (dB) form:

\[ \text{Received Power (dBm)} = \text{Transmitted Power (dBm)} + \text{Gains (dB)} - \text{Losses (dB)} \]

Because decibels are logarithmic units, adding gains and subtracting losses is equivalent to multiplying actual power ratios.

RF Link Budget Formula

P_RX = P_TX + G_TX – L_TX – L_FS – L_M + G_RX – L_RX

Parameter	Description
P_RX	Received Power (dBm)
P_TX	Transmitter Output Power (dBm)
G_TX	Transmitter Antenna Gain (dBi)
L_TX	Transmitter Cable/Connector Loss (dB)
L_FS	Free-Space Path Loss (dB)
L_M	Miscellaneous Losses (fade margin, polarization, rain)
G_RX	Receiver Antenna Gain (dBi)
L_RX	Receiver Cable/Connector Loss (dB)

Free Space Path Loss

The path loss is the loss due to propagation between the transmitting and receiving antennas and is usually the most significant contributor to the losses, and also the largest unknown. When transmitting through, it can be expressed in a dimensionless form by normalizing the distance to the wavelength:

General wavelength-based form:

\[ L_{FS}(dB) = 20 \log_{10} \left( 4\pi \frac{d}{\lambda} \right) \]

Engineering form (MHz & km):

\[ L_{FS}(dB) \approx 32.45 + 20\log_{10}(f_{MHz}) + 20\log_{10}(d_{km}) \]

Link Margin

\[ \text{Link Margin} = P_{RX} - \text{Receiver Sensitivity} \]

Link margin provides a safety buffer to ensure reliable communication under fading, atmospheric loss, and environmental variations.

Optical Link Budget (Fiber Systems)

\[ L_T = \alpha L + L_c + L_s \]

L_T – Total Loss
α – Fiber Attenuation (dB/km)
L – Fiber Length
L_c – Connector Loss
L_s – Splice Loss

Why Link Budget Is Important

Link budget calculations are essential in:

5G NR and LTE network planning
Microwave backhaul design
Satellite communication
WiFi coverage planning
Deep space communication
Fiber optic systems

Without a proper link budget, networks may suffer from:

Poor coverage
Frequent call drops
Low throughput
High packet loss
Unstable links in rain or fading conditions

A well-designed link budget ensures predictable and stable performance.