Link Budget Calculator
Estimate EIRP, maximum path loss and cell range using Free-Space Path Loss (FSPL) model.
Range uses FSPL only — no terrain or clutter correction. Use the Path Loss tool for Okumura-Hata estimates.
Link Budget Formulas
A link budget accounts for every gain and loss between transmitter and receiver to determine whether a radio link is viable.
EIRP = PTX + GTX − LTX
MAPL = EIRP − SRX + GRX − LRX − Mshadowing − Minterference
FSPL = 20·log₁₀(dkm) + 20·log₁₀(fMHz) + 32.44 [dB]
dkm = 10 ^ ((MAPL − 20·log₁₀(f) − 32.44) / 20)
EIRP = Effective Isotropic Radiated Power · MAPL = Maximum Allowable Path Loss · SRX = RX sensitivity · M = margin
Transmit power (PTX) is entered in dBm. For a realistic terrestrial path loss to use as propagation input, see the path loss calculator with Okumura-Hata or COST-231 models.
Worked Example — LTE 1800 MHz Macro Downlink
A typical urban LTE deployment on Band 3 (1800 MHz). Calculate EIRP, MAPL, and estimated FSPL range.
| Parameter | Value | Notes |
|---|---|---|
| TX power (P_TX) | +43 dBm | Typical LTE macro eNB, 20 W per port |
| TX antenna gain (G_TX) | +18 dBi | 65° sector antenna, 4×4 MIMO panel |
| TX cable / filter loss | −2 dB | Feeder + jumper + connector |
| EIRP | +59 dBm | 43 + 18 − 2 = 59 dBm (794 W) |
| RX sensitivity (S_RX) | −100 dBm | LTE Cat-4 UE, 10 MHz BW, QPSK |
| RX antenna gain (G_RX) | 0 dBi | Handset internal antenna |
| Shadowing margin | −8 dB | 8 dB for 90 % edge coverage |
| Interference margin | −3 dB | Frequency reuse, neighbouring cells |
| MAPL | 148 dB | 59 − (−100) + 0 − 8 − 3 = 148 dB |
| FSPL range @ 1800 MHz | ≈ 4.5 km | FSPL only — apply Hata for real range |
The FSPL range of 4.5 km assumes clear line-of-sight. For urban macro propagation, apply Okumura-Hata path loss instead — typical urban range drops to 1.5–3 km at 148 dB MAPL on 1800 MHz. For transmit power in other units, use the dBm converter.
Frequently Asked Questions
What is EIRP?▾
EIRP (Effective Isotropic Radiated Power) is the total power that an antenna would need to radiate isotropically (in all directions equally) to produce the same signal strength in the main beam direction. It equals transmitter power plus antenna gain minus cable and connector losses. EIRP determines how strong your signal appears to a receiver.
What is MAPL?▾
MAPL (Maximum Allowable Path Loss) is the largest propagation loss the radio link can tolerate while still meeting the minimum required signal level at the receiver. It is calculated as EIRP minus RX sensitivity plus RX antenna gain, minus all fade and interference margins. Higher MAPL means longer potential range.
Why is the FSPL-based cell range unrealistically large?▾
Free-Space Path Loss assumes a clear line of sight with no obstructions — ideal for satellite links but not urban ground-level cells. Real deployments add 20–40 dB of excess loss from buildings, terrain, and vegetation. Use the Path Loss tool with Okumura-Hata for realistic terrestrial range estimates.
What is a typical LTE macro link budget?▾
A typical 1800 MHz LTE macro downlink budget: TX power 43 dBm + antenna gain 18 dBi − cable loss 2 dB = EIRP 59 dBm. RX sensitivity −100 dBm + RX gain 0 dBi − shadowing 8 dB − interference 3 dB gives MAPL ≈ 148 dB. With Okumura-Hata urban corrections this corresponds to roughly 2–4 km cell radius.