This tool computes the maximum range that can be achieved in a communication system. It uses the **Free Space Path Loss** **(FSPL) **equations.

The system includes a transmitter, transmit antenna, receiver and receive antenna.

To calculate the max distance, enter the following:

- Frequency of operation (Hz/KHz/MHz/GHz)
- Transmit Power (dBm)
- Transmit Antenna Gain (dBi)
- Receiver Sensitivity (dBm)
- Receive Antenna Gain (dBi)
- Total Cable and Other Losses (dB)

**Formula**

The calculator uses the Free Space Path Loss (FSPL) equation:

**FSPL = 20*Log _{10}(d) + 20*Log_{10}(f) + L_{c} + 20*Log_{10}(4π/c) – G_{Tx} – G_{Rx}**

**Example Range Calculation**

At a frequency of 2450 MHz (ISM band) and transmit power of +20 dBm, let’s take a look at the range of a Wi-Fi Access point in **free space**.

With a receiver sensitivity of -90 dBm, transmit and receive antenna gain of 0 dBi, and 0 dB cable loss, the maximum range is** 3.1 km** or** 1.9 miles.**

Important to remember that this calculation is outdoors and free space which represents **an ideal signal propagation condition**.

The free space path loss calculator assumes ideal conditions. In other words there is an assumption of no obstructions and no radio interference from neighboring access points or other ISM band devices. For a more realistic estimate of indoor Wi-Fi range, use this calculator

Assuming indoor conditions, using the indoor calculator, the same level of received signal is achieved at only **55 meters**. A much smaller range. This is to be expected as signals are attenuated more indoors than in free space.

**How to use the calculator**

Below is a list of the terms used in the calculator and what each of them mean.

**Frequency of operation**

This is the frequency at which the communication system operates.

**Transmit Power**

This is the power at the output connector of the transmitter. It is usually specified in dBm. However many vendors specify this quantity in Watt. Use this calculator to convert from Watt to dBm.

**Transmit Antenna Gain**

This depends on the type of antenna used and is expressed in dBi (dB relative to isotropic antenna).

**Receiver Sensitivity**

Minimum level of input signal that a radio receiver can detect and demodulate. Use this calculator to find the sensitivity as a function of temperature, SNR and receiver noise figure.

**Receive Antenna Gain**

Depends on antenna used and is expressed in dBi. In cases where the signal is from a particular direction, a high gain antenna (8 dBi for instance) can be used. This allows focusing of energy instead of receiving from all directions. It can be calculated from the Antenna Factor and frequency of operation

**Total Cable and Other Losses**

This includes losses between connectors and antennas. If RF Splitters are used, the loss should be accounted for as well. It is specified in dB. Use this calculator to find the loss due to antenna cable.