Calculate a complete wireless link budget from transmitter to receiver. Input all gains and losses to determine whether your signal will arrive above the receiver sensitivity threshold. Essential for planning wireless bridges, long-range WiFi, and point-to-point links.
A link budget is a comprehensive accounting of all gains and losses in a wireless communication system — from the transmitter's power output through the antennas, cables, and free space, all the way to the receiver's input. It answers the fundamental question: will the signal arrive at the receiver above its minimum sensitivity threshold?
Link budgets are essential for planning any wireless connection — from a simple home router setup to multi-kilometer wireless bridge links. If your WiFi coverage analysis shows marginal signal at certain locations, a link budget tells you exactly where the bottleneck is and how to fix it.
The complete link budget formula accounts for every element in the RF chain:
Received Power (dBm) = Tx Power + Tx Antenna Gain - Tx Cable Loss
- FSPL - Additional Losses
+ Rx Antenna Gain - Rx Cable Loss
Fade Margin = Received Power - Receiver SensitivityA positive fade margin means the link works. For reliable operation, you need at least 10 dB of fade margin to account for weather, interference, and equipment aging. Use our FSPL Calculator for the path loss component and the Antenna Gain Calculator for EIRP.
Fade margin is the safety buffer between your expected received signal and the minimum required. Environmental conditions cause signal fluctuation (fading), and the margin ensures your link survives these variations:
| Fade Margin | Link Reliability | Availability | Suitable For |
|---|---|---|---|
| 0-3 dB | Borderline | ~90% | Testing only, not production |
| 3-10 dB | Marginal | ~99% | Non-critical links, backup |
| 10-15 dB | Good | ~99.9% | Standard production links |
| 15-25 dB | Excellent | ~99.99% | Critical infrastructure |
| 25+ dB | Over-engineered | ~99.999% | Usually means shorter distance possible |
Pro Tip: For outdoor links, always target at least 15 dB of fade margin. Rain, humidity, and temperature changes can cause 5-10 dB of signal variation throughout the year. For indoor WiFi, a 10 dB margin above -67 dBm (the threshold for reliable HD streaming) is sufficient. Check real-world performance with a speed test and signal strength measurements.
Use these typical values when planning your link. For precise numbers, consult your equipment datasheets. Our Antenna Gain Calculator provides detailed antenna specifications:
| Component | Typical Range | Best Practice |
|---|---|---|
| Router Tx Power | 14-23 dBm | Use actual spec, not max |
| Outdoor Radio Tx Power | 20-27 dBm | Verify regulatory compliance |
| Omni Antenna | 2-8 dBi | Good for broad coverage |
| Directional Antenna | 10-30 dBi | Essential for point-to-point |
| LMR-400 Cable Loss (per 100ft @ 5 GHz) | 10.8 dB | Keep runs short |
| WiFi Receiver Sensitivity | -65 to -95 dBm | Lower is more sensitive |
| Connector Loss (each) | 0.2-0.5 dB | Minimize connectors |
Here are typical link budgets for common wireless scenarios. These give you a starting point for your own calculations:
| Scenario | Distance | Freq | Tx EIRP | FSPL | Rx Gain | Received | Margin |
|---|---|---|---|---|---|---|---|
| Home WiFi (router to phone) | 15 m | 5 GHz | 23 dBm | 70 dB | 0 dBi | -47 dBm | 18 dB |
| Office AP to laptop | 30 m | 5 GHz | 27 dBm | 76 dB | 3 dBi | -46 dBm | 19 dB |
| Short outdoor bridge | 1 km | 5.8 GHz | 42 dBm | 108 dB | 24 dBi | -44 dBm | 36 dB |
| Medium bridge | 5 km | 5.8 GHz | 42 dBm | 122 dB | 24 dBi | -58 dBm | 22 dB |
| Long-range bridge | 20 km | 5.8 GHz | 42 dBm | 134 dB | 30 dBi | -64 dBm | 16 dB |
When your link budget shows insufficient margin, these strategies improve the result. Each 3 dB of improvement effectively doubles signal power or doubles range:
After making changes, verify real-world performance with ping tests and speed tests. For WiFi specifically, selecting the right channel with a WiFi channel finder can eliminate interference-related losses that don't appear in link budgets.
While link budgets are traditionally associated with outdoor point-to-point links, the same principles apply to indoor WiFi. For router placement planning, the main differences are wall losses and multi-path effects:
If your indoor link budget is marginal, explore extending WiFi range, setting up access points, or connecting additional routers. The Bandwidth Calculator helps determine if the resulting signal level supports your required throughput.
For production links, 10-15 dB is standard. Critical infrastructure links should have 15-25 dB to handle weather variations, equipment aging, and occasional Fresnel zone intrusion from vegetation growth. Under 3 dB means the link will be unreliable.
Because there are two antennas — one at the transmitter and one at the receiver. The Tx antenna focuses the signal toward the receiver (Tx gain), and the Rx antenna captures more of the incoming signal than an isotropic antenna would (Rx gain). Both contributions are additive in dB.
Yes. For indoor WiFi, add wall losses to the "Additional Loss" field. Use typical values: 3 dB for drywall, 8 dB for brick, 12 dB for concrete per wall. Set Rx sensitivity to your device's spec (phones are typically -65 to -70 dBm). Our WiFi Coverage Estimator simplifies this process.
EIRP (Effective Isotropic Radiated Power) is the effective power leaving your antenna system: Tx Power minus cable loss plus antenna gain. It represents the total radiated power as if it came from a perfect omnidirectional antenna. The Antenna Gain Calculator computes this for you.
Distance affects only the FSPL component. Doubling the distance adds 6 dB of path loss. This means to double range while maintaining the same fade margin, you need 6 dB more system gain (bigger antennas or more transmit power).
Receiver sensitivity is the minimum signal level a radio can decode successfully, measured in dBm. A more sensitive receiver (lower dBm value, like -95 dBm vs -75 dBm) can detect weaker signals, allowing longer range or more fade margin. Higher data rates require stronger signals.
For frequencies below 10 GHz (including all WiFi bands), rain fade is minimal — usually under 1 dB. For millimeter wave links (24 GHz, 60 GHz), heavy rain can add 5-20 dB of loss and must be included. Add rain fade to the "Additional Loss" field.
About Tommy N.
Tommy is the founder of RouterHax and a network engineer with 10+ years of experience in home and enterprise networking. He specializes in router configuration, WiFi optimization, and network security. When not writing guides, he's testing the latest mesh WiFi systems and helping readers troubleshoot their home networks.
 |
 |
 |
 |
Promotion for FREE Gifts. Moreover, Free Items here. Disable Ad Blocker to get them all.
Once done, hit any button as below
|
|
|
|