Link Budget Calculator
A link budget tracks signal power from transmitter to receiver, accounting for every gain and loss in the chain. The output is link margin — how much signal headroom exists above the minimum detectable level. Positive margin = link closes; negative = it won't work.
Equations & Parameters ▸
\(\text{Margin} = P_t + G_t + G_r - L_{total} - \text{FSPL} - N_{floor} - \text{SNR}_{req}\)
| Pₜ | Transmit power (dBm). |
| Gₜ, Gᵣ | Transmit and receive antenna gains (dBi). |
| Lₜₓ, Lᵣₓ | Cable/connector losses at TX and RX (dB, enter as positive loss). |
| d | Link distance (m). |
| NF | Receiver noise figure (dB). |
| BW | Receiver bandwidth (Hz). Noise floor = −174 + NF + 10·log₁₀(BW) dBm. |
| SNR_req | Required SNR at receiver for acceptable performance (dB). |
Physical constants used
| c | Speed of light = 2.998×10⁸ m/s |
| µ₀ | Permeability of free space = 4π×10⁻⁷ H/m ≈ 1.2566×10⁻⁶ H/m |
| ε₀ | Permittivity of free space = 8.854×10⁻¹² F/m |
| k_B | Boltzmann constant = 1.381×10⁻²³ J/K |
| h | Planck constant = 6.626×10⁻³⁴ J·s |
| ¹H gyromagnetic ratio | γ/2π = 42.577 MHz/T |
Inputs
dBm
dBi
dBi
dB
Cable + connectors at TXdB
Cable + connectors at RXdB
Pointing, polarisation, etc.m
dB
dB
Minimum for demodulationResults
Diagram