RF Link Budget Calculator

Enter Tx power, antenna gains, and losses to calculate received signal level and link margin.

Link Budget

Tx Power transmitter output power

dBm

Tx Antenna Gain dBi (0 = isotropic)

dBi

Tx Cable / Feed Loss enter as positive dB

Path Loss free space or measured total

Frequency

GHz

Distance

Rx Antenna Gain dBi (0 = isotropic)

dBi

Rx Cable / Feed Loss enter as positive dB

Rx Sensitivity minimum detectable signal (optional)

dBm

EIRP Effective Isotropic Radiated Power

—

Received Signal Level at Rx input

—

Link Margin positive = link OK

—

EIRP = P_tx + G_tx − L_tx

FSPL = 20log(f) + 20log(d) + 92.45

f in GHz, d in km

RSL = EIRP − L_path + G_rx − L_rx

Margin = RSL − Sensitivity

All values in dB / dBm / dBi. Losses entered as positive dB values. FSPL formula: Friis free space path loss for 1 GHz at 1 km ≈ 92.45 dB.