What is Wi-Fi signal strength measured in: units, standards, and definitions

When you notice videos on your smartphone loading choppily or games lagging, the first thing that comes to mind is poor internet. However, the problem often lies not with your ISP speed, but with the physical level of your wireless connection. To understand the actual network status, it's not enough to simply look at the "bars" in the corner of your device's screen, as this indicator is highly subjective and can vary greatly from device to device.

Professional diagnostics require precise digital data that allows us to determine how much radio signal attenuation occurs when passing through walls and ceilings. The key parameter here is received signal level, which has a clear physical expression. Understanding how it is calculated and interpreted allows you to objectively assess the quality of the coating in your apartment or office.

In this article, we'll explore the basic units of measurement, learn how to translate abstract values ​​into understandable quality indicators, and discover what thresholds are considered normal for the stable operation of modern communications standards.

Basic unit of measurement: dBm

The absolute standard in the world of wireless communications is the value dBm (decibel milliwatt). This is a logarithmic unit of power measurement that shows the ratio of signal strength to a reference value of 1 milliwatt. A unique feature of this scale is that it is always negative, since the Wi-Fi signal strength reaching the receiver is typically significantly less than one milliwatt.

Many users mistakenly believe that the higher the number, the better, forgetting about the minus sign. In reality, the closer the value is to zero, the stronger the signal. For example, the indicator -40 dBm means that you are almost right next to the router, and the value -90 dBm indicates that the connection is about to be lost. A difference of just 3 dBm represents a twofold change in power, making this scale very sensitive to changes in the environment.

⚠️ Attention: Don't confuse dBm (power) with dBi (antenna gain). While transmitter power is measured in dBm, the router's antenna gain is measured in dBi. Increasing dBi narrows the beam pattern, making the signal longer-range but less wide-ranging.

To accurately understand connection quality, it's important to consider that different chipsets in smartphones and laptops can show a 3-5 dBm difference under identical conditions. Therefore, it's best to use the same device or specialized calibration equipment when taking measurements.

Alternative metrics: RSSI, ASU, and connection quality

In addition to absolute power in dBm, operating systems and networking equipment often use relative metrics. One of the most common is RSSI (Received Signal Strength Indicator). This is an indexed parameter that chip manufacturers (Intel, Qualcomm, Broadcom) define differently. Typically, the RSSI scale ranges from 0 to 100 or 0 to 60, with a higher number indicating a better signal.

Another important metric, especially for Android mobile devices, is ASU (Arbitrary Strength Unit). This is an integer value that is directly converted to dBm using the formula: Power (dBm) = -113 + (2 × ASU)Knowing this formula, you can easily convert obscure numbers from your phone's engineering menu into familiar decibels.

• 📶 RSSI — a relative indicator depending on the adapter manufacturer, often used by drivers to switch between access points.
• 📱 ASU — a standardized parameter for cellular networks and Wi-Fi on Android, allowing for unification of data from different vendors.
• 📉 SNR (Signal-to-Noise Ratio) is the signal-to-noise ratio, a critical parameter that shows how much more powerful the useful signal is than the background noise.

It's important to understand that a high RSSI or ASU alone won't guarantee high speed if the airwaves are cluttered by neighboring routers. That's why signal-to-noise ratio is often more important than absolute power. If your signal -60 dBm, but the noise level is -65 dBm, there will be no stable operation, despite the seemingly good reception level.

Interpretation of values: signal level table

To avoid guessing whether your signal is good, it's important to compare the received data with generally accepted quality standards. Different sources may have slightly different limits, but the physics of the process remain the same: signal attenuation in space occurs exponentially. Below is a detailed table to help you classify the condition of your network.

Please note that for the range 5 GHz The requirements for the signal level are more stringent due to the lower penetrating power of waves of this frequency. -70 dBm For 5 GHz it may already be a "dead zone", while for 2.4 GHz it is still a working, although not ideal, signal.

Factors Affecting Signal Attenuation

Why does the signal weaken even if you're just a few meters away from the router? Physical obstacles are the main enemy of a wireless network. Building materials absorb and reflect radio waves differently. Metal reinforcement in walls, mirrors with amalgam coatings, and even aquariums can block up to 90% of radiation.

In addition to building structures, a huge role is played by sources of electromagnetic interferenceMicrowave ovens operating at 2.4 GHz, wireless baby monitors, Bluetooth headsets, and even string lights with cheap drivers create a "mess" in the airwaves, which reduces the effective power of the useful signal.

• 🧱 Walls: Concrete with reinforcement dampens the signal the most, while wood and plasterboard transmit waves much better.
• 💧 Water: The human body and houseplants also contain water and can make adjustments if they are in the path of the beam.
• 📡 Neighbours: Overlapping channels with neighboring routers creates interference, which is perceived by the device as a decrease in signal quality.

There's also the multipath effect, where the signal doesn't reach the receiver directly, but rather after being reflected off walls and furniture. These reflected copies of the signal can arrive with a delay and cancel out the main signal, causing errors in the data packet.

⚠️ Attention: Avoid placing your router near a microwave oven or on the floor behind a sofa. The metal housing of the appliance and soft-filled furniture can reduce the effective range of the network by half.

Diagnostics and measurements: how to obtain accurate data

To conduct a professional signal level measurement, simply checking Windows or macOS settings isn't enough, as they often only display an average value. It's best to use specialized software that can generate heat maps and display dBm dynamics in real time.

On Windows computers, a great tool is the console utility netshIt allows you to get a detailed report on your current connection without installing any third-party software. To launch, open the command prompt (CMD) as an administrator and enter the following command:

netsh wlan show interfaces

In the list that appears, find the "Signal" line, where the value will be shown as a percentage. While this isn't dBm, it can be roughly calculated: 100% is about -50 dBm, and 0% is about -100 dBm. For a more in-depth analysis on Android, use apps like Wi-Fi Analyzer or Network Cell Info, which will show the exact value in dBm and a channel loading graph.

When taking measurements, it's important to hold the device in your hand rather than placing it on a table, as the human body also affects the smartphone's antenna pattern. Walk along the route you use most often and notice any sharp drops in the graph.

Methods for improving reception and optimization

If measurements show that the signal level in important areas is lower -75 dBm, action is necessary. The simplest and most often overlooked method is to reposition the router. Raise it higher, remove it from its niches, and deploy the antennas vertically (for horizontal coverage) or fan them out if you need to cover multiple floors.

If rearranging your furniture doesn't help, consider upgrading your equipment. Older 802.11n routers have less sensitive receivers and weaker amplifiers than modern Wi-Fi 6 models. Replacing the device can boost signal strength by 5-10 dBm simply due to improved electronics.

• 🔄 Change channel: Switching to a less crowded channel can improve SNR even if the signal strength (dBm) remains the same.
• 📡 External antennas: If your router allows it, replacing the standard antennas with models with a higher gain (dBi) will improve reception.
• 🏠 Mesh systems: For large apartments and houses, the best solution is to install a system of several modules that create a single seamless network.

Why do repeaters often make the situation worse?

Repeaters receive the signal and transmit it further, but they do so in half-duplex mode and often cut the speed in half. Furthermore, they can create additional interference if they are located in an area with an already weak signal, simply transmitting the noise further.

In challenging architectural settings, where the walls are too thick, the only solution is to run cable (twisted pair) to distant rooms and install additional access points there. This ensures that each point in the room has its own strong signal source.

Why is the signal good on one device and bad on another?

This is due to differences in receiver sensitivity (RX sensitivity) and antenna design. A flagship smartphone may have four MIMO antennas and a powerful chip, while a budget tablet may have a single weak antenna. Furthermore, cases with metal components can shield the signal on a specific device.

Does the number of connected devices affect the signal level (dBm)?

No, the number of devices does not affect the physical strength of the received signal (dBm). However, it does affect channel throughput and increases latency (ping). If there are many devices, the router may not be able to process requests quickly, creating the illusion of "bad internet," even though the signal strength remains stable.

Can weather affect indoor Wi-Fi?

There's no direct impact on short-range indoor signals. However, a strong thunderstorm with static discharges can create powerful electromagnetic pulses, causing short-term interference. Also, high humidity in the air (fog, heavy rain) theoretically absorbs the 5 GHz signal more strongly, but at the scale of an apartment, this effect is imperceptible.