Ubiquiti Calculator

Plan your Ubiquiti airMAX, airFiber, or UniFi PtP/PtMP links by estimating signal strength, link quality, and Fresnel zone clearance before deployment.

Chart: Visual representation of the link budget components.

Signal Strength (RSSI)	Modulation (MCS)	Theoretical Throughput	Link Quality

Table: Estimated throughput based on calculated signal strength. Actual speeds may vary due to interference and other factors.

What is a Ubiquiti Calculator?

A Ubiquiti Calculator is an essential planning tool for network engineers and IT professionals who design and deploy wireless networks using Ubiquiti hardware, such as the airMAX, airFiber, and UniFi product lines. Specifically, this calculator focuses on modeling Point-to-Point (PtP) and Point-to-Multipoint (PtMP) links. It mathematically simulates the performance of a wireless bridge before any hardware is installed, saving significant time and resources. By inputting key variables like distance, frequency, and equipment power, users can predict critical performance metrics. This foresight is crucial for ensuring a stable, high-throughput connection between two or more locations.

This tool is invaluable for anyone from a seasoned wireless internet service provider (WISP) planning a new tower, to a business needing to connect two office buildings, or a homeowner wanting to extend their network to a workshop. The primary goal of a Ubiquiti Calculator is to move beyond guesswork and apply radio frequency (RF) science to real-world deployment scenarios.

Common Misconceptions

A frequent misconception is that simply having a clear line of sight is enough for a strong wireless link. However, a Ubiquiti Calculator demonstrates the importance of the Fresnel Zone—an elliptical area around the line of sight that must also be clear of obstructions. Another common error is underestimating the impact of distance and frequency on signal loss, a factor this calculator quantifies as Free Space Path Loss (FSPL).

Ubiquiti Calculator Formula and Mathematical Explanation

The core of this Ubiquiti Calculator revolves around the link budget formula, which sums all gains and subtracts all losses to determine the final signal strength at the receiver. The primary components are Transmit Power, Antenna Gain, and Free Space Path Loss.

The step-by-step calculation is as follows:

1. Calculate Free Space Path Loss (FSPL): This is the largest source of signal loss in a wireless link. The formula is:
   FSPL (dB) = 20*log10(distance_km) + 20*log10(frequency_MHz) + 92.45
2. Calculate Received Signal Strength (RSSI): This is the final signal level the receiving radio “hears”. The formula is:
   RSSI (dBm) = TxPower + TotalAntennaGain - FSPL - CableLoss
3. Calculate Link Margin: This buffer indicates the robustness of the link. It’s the difference between the received signal and the receiver’s sensitivity:
   Link Margin (dB) = RSSI - ReceiverSensitivity

A positive link margin is required for a connection, and a margin of 15 dB or more is recommended for reliability.

Variables Table

Variable	Meaning	Unit	Typical Range
Distance	The physical distance of the wireless link.	km	0.1 – 100
Frequency	The radio frequency band of operation.	MHz	2400 / 5800 / 60000
Tx Power	The output power of the transmitting radio.	dBm	0 – 27
Antenna Gain	The signal amplification provided by the antennas.	dBi	6 – 34
RSSI	Received Signal Strength Indicator.	dBm	-30 (Excellent) to -85 (Poor)

Practical Examples (Real-World Use Cases)

Example 1: Connecting Two Office Buildings

A company needs to link its main office to a new warehouse 2.5 km away. They plan to use Ubiquiti NanoStation 5AC units, which operate in the 5 GHz band.

• Inputs:
  • Distance: 2.5 km
  • Frequency: 5800 MHz
  • Transmit Power: 20 dBm
  • Antenna Gain (2x 16 dBi): 32 dBi
  • Cable Loss: 1 dB
• Outputs from Ubiquiti Calculator:
  • FSPL: ~116.4 dB
  • Expected RSSI: -65.4 dBm
  • Link Margin (with -94 dBm sensitivity): ~28.6 dB
• Interpretation: An RSSI of -65.4 dBm is a strong signal, promising high throughput and reliability. The healthy link margin confirms the link will be stable even with minor environmental fluctuations. For more details on equipment, see our airMAX Hardware Guide.

Example 2: Rural WISP Deployment

A Wireless ISP is evaluating a potential customer located 8 km from their tower. They are considering using a LiteBeam AC Gen2.

• Inputs:
  • Distance: 8 km
  • Frequency: 5800 MHz
  • Transmit Power: 22 dBm
  • Antenna Gain (2x 23 dBi): 46 dBi
  • Cable Loss: 2 dB
• Outputs from Ubiquiti Calculator:
  • FSPL: ~124.5 dB
  • Expected RSSI: -58.5 dBm
  • Fresnel Zone Radius: ~7.2 meters (This must be clear of trees and buildings)
• Interpretation: The calculated RSSI of -58.5 dBm is excellent, indicating a high-performance link is possible. The critical factor here is the Fresnel Zone. The WISP must perform a site survey to ensure no obstructions encroach upon the 7.2-meter radius at the link’s midpoint. This analysis is a core function of a reliable Ubiquiti Calculator. Learn more about surveys in our RF Line of Sight Tool.

How to Use This Ubiquiti Calculator

Using this tool is a straightforward process designed to give you actionable results quickly. Follow these steps for an accurate link performance analysis.

1. Enter Link Distance: Input the total distance between your two radio points in kilometers.
2. Select Frequency: Choose the appropriate frequency band for your hardware (e.g., 5.8 GHz for most modern Ubiquiti airMAX gear).
3. Input Transmit Power: Find the transmit power (in dBm) from your radio’s datasheet.
4. Enter Antenna Gain: Add the gain (in dBi) of the antenna on the transmitting side and the receiving side. For integrated units like a NanoStation, this is a single value from the datasheet used for both. For dish antennas, use the dish’s gain.
5. Set Receiver Sensitivity: This value, found on the datasheet, determines the minimum signal needed. The default is a good starting point for most Ubiquiti radios.
6. Account for Cable Loss: For any link using external antennas, estimate 1-3 dB of loss for pigtail cables and connectors.
7. Read the Results: The Ubiquiti Calculator automatically updates the RSSI, Link Margin, and Fresnel Zone. Use the RSSI to check the throughput table for expected performance.

Decision-Making Guidance: An RSSI between -40 dBm and -65 dBm is ideal. If your signal is weaker than -75 dBm, consider using higher-gain antennas or reducing the link distance. A link margin below 10 dB is risky and may be unstable. For complex scenarios, consult our Advanced Link Planning Guide.

Key Factors That Affect Ubiquiti Calculator Results

• Line of Sight (LoS): This is non-negotiable. There must be a clear visual path between the two antennas.
• Fresnel Zone Clearance: As crucial as LoS, the area around the signal path must be clear. Obstructions like trees or buildings in the Fresnel Zone will degrade or block the signal. Our Ubiquiti Calculator helps quantify the clearance needed.
• RF Interference: Other wireless networks operating on the same or adjacent frequencies can severely impact performance. Use tools like Ubiquiti’s airView to find a clean channel.
• Antenna Gain: This is the most effective way to improve signal over a long distance. Doubling the distance requires a 6 dB increase in antenna gain to maintain the same signal strength.
• Transmit Power: While important, increasing power is often not the best solution. It can increase interference for others and may be limited by regulations. It’s often better to improve antenna gain.
• Weather (Rain Fade): Heavy rain can absorb RF energy, weakening the signal. This is especially true for higher frequencies like 60 GHz, but can also affect 5 GHz links. A strong link margin (20+ dB) is essential for all-weather reliability. Explore our Weather Impact Model.

Frequently Asked Questions (FAQ)

1. What is a good RSSI for a Ubiquiti link?
An RSSI of -40 dBm to -65 dBm is considered excellent to very good. Links between -66 dBm and -75 dBm are generally reliable but may have lower throughput. Anything below -80 dBm is likely to be unstable.

2. Can this Ubiquiti Calculator be used for UniFi Building-to-Building Bridges?
Yes. The principles are the same. For a UBB, you would typically use the 60 GHz frequency for the main link and 5 GHz for the backup, entering the respective specs for each calculation.

3. Why is my actual signal different from the calculator’s estimate?
This Ubiquiti Calculator computes ideal “free space” loss. The real world includes RF interference, atmospheric conditions, and minor obstructions that can alter the result. It provides a baseline, not a guarantee.

4. How much of the Fresnel Zone needs to be clear?
For an optimal link, at least 60% of the first Fresnel Zone’s radius should be completely clear of any obstructions. Ideally, 100% clearance is desired.

5. Does antenna alignment matter?
Absolutely. High-gain antennas have very narrow beamwidths. Even a few degrees of misalignment can cause a massive loss in signal. The values in this Ubiquiti Calculator assume perfect alignment.

6. What is the difference between dBm, dBi, and dB?
dBm is a unit of power (relative to 1 milliwatt). dBi is a measure of antenna gain (relative to an isotropic antenna). dB is a generic ratio used for losses and gains (like cable loss or link margin).

7. Why can’t I just increase my transmit power to the max?
Maximum power is limited by regulations (e.g., FCC, ETSI) and can create unwanted noise for your own and other networks. A well-designed link is a balance of power and gain. See our RF Fundamentals Guide.

8. How does frequency choice impact my link?
Lower frequencies (like 2.4 GHz) travel further and are less affected by minor obstacles, but are often more crowded with interference. Higher frequencies (5 GHz, 60 GHz) offer more bandwidth and less interference but suffer greater signal loss over distance and through obstacles.

Related Tools and Internal Resources

• UniFi Protect Storage Calculator: Plan the storage requirements for your surveillance system based on camera count and retention policies.
• Network Latency Calculator: Understand the sources of delay in your network infrastructure.
• Beginner’s Guide to Setting Up a PtP Link: A step-by-step walkthrough of the physical installation and software configuration process.