WiFi signal level (dBm): full explanation and standards

Internet connection speeds are often disappointing, even if you're paying your provider for a high-bandwidth plan. In most cases, the problem isn't with the cable running into your apartment, but with the quality of the wireless connection between your router and your device. To understand the quality of this connection, a technical unit of measurement is used. dBm (decibel-milliwatt), which shows the actual power of the radio signal.

Many users only see "sticks" on their smartphone screen, but this is an extremely inaccurate indicator that hides the real picture. Understanding what it is dBm WiFi, allows you to objectively assess network coverage, identify dead zones in your home, and properly configure your equipment. Unlike abstract icons, the numerical value provides a precise indication of how well your device is hearing the router.

In this article, we'll take a detailed look at the physics behind the process, normal values, and practical ways to improve reception. You'll learn why negative numbers are normal and how to turn an unstable internet connection into a reliable channel for work and entertainment.

Physics of the process: why are the values ​​negative?

Unit of measurement dBm It represents the logarithmic ratio of signal power to one milliwatt. Since the WiFi signal attenuates with distance from the source and its power becomes less than the reference milliwatt, the logarithm of this ratio is negative. This is why you always see values ​​with a minus sign in operating system interfaces, for example, -65 dBm.

The key principle to remember is that the closer the value is to zero, the stronger the signal. This means that -40 dBm is a great, powerful signal, while -90 dBm means virtually no connection. A difference of just a few dBm can dramatically change data transfer speed and ping.

There's a physical limit to the sensitivity of WiFi receivers. If the signal strength drops below -90 dBm or -95 dBm, the device simply stops "hearing" the network and drops the connection. This is why internet connection can be lost completely in remote corners of a house or through thick concrete walls.

⚠️ Important: Don't confuse dBm with dBi. While dBm is the current signal strength, dBi is the antenna gain. Buying a high-dBi antenna doesn't guarantee a stronger signal if the router itself is weak.

Understanding this logarithmic scale helps avoid diagnostic errors. Increasing the router's transmit power doesn't always improve the situation linearly, as the response signal from the smartphone to the router may remain weak due to the mobile device's low battery.

Table of signal levels and their impact on operation

To understand the numerical values, it's necessary to know the thresholds for various tasks. The digital gap between "good" and "bad" may be only 10-15 units, but it will feel like a complete network failure.

As the table shows, the comfort zone is in the range of up to -65 dBm. If your measurements show values ​​below -70 dBm in the locations where you plan to work, you should consider network optimization.

It is important to take into account that there are different WiFi standards (802.11n, ac, ax) may behave differently at the edge of the coverage area. Newer standards often require a cleaner signal to operate at maximum speeds, falling back to lower speeds as conditions deteriorate.

How to measure signal strength on different devices

Operating systems hide or display technical network information in different ways. To obtain accurate data dBm You need to use built-in tools or third-party software.

On devices Android Information is often hidden in engineering menus. The easiest way is to use specialized analysis applications that visualize data in real time.

• 📱 WiFi Analyzer: A popular app that shows a signal graph and level in dBm as you move around the room.
• 📡 Network Cell Info: a more professional tool with detailed statistics and graphs.
• 🔍 Fing: network scanner that also displays the quality of the connection to the current access point.

For users iOS (iPhone, iPad) accessing this data is more difficult due to system limitations. The standard method is to use a utility AirPort Utility from Apple. You need to install the app, then go to iPhone settings, find AirPort and turn on the "WLAN Scanner" toggle switch. After this, the app will display the RSSI (signal strength) in dBm during scanning.

On computers running Windows You can use the command line. Open the terminal and enter the command:

netsh wlan show interfaces

In the list that appears, find the line “Signal”, where the percentage value can be roughly converted to dBm, or use third-party utilities like Acrylic Wi-Fi for more accurate data.

⚠️ Important: When measuring, hold the device in the same position you normally use the internet. Smartphone antennas are often located at the bottom or top of the device, and holding the device can change the reading by 5-10 dBm.

Factors Affecting Signal Attenuation

A WiFi signal is a radio wave that is susceptible to environmental influences. Even if the router is powerful, the physical environment can absorb all the signal energy before it reaches the receiver.

Walls and ceilings are the main enemies. The materials they are made of have varying degrees of radio wave absorption. Metal reinforcement in concrete or foil-clad insulation can act as a shield, completely blocking the signal.

• 🧱 Concrete walls: attenuate the signal by 10-15 dBm each.
• 🪟 Glass (especially coated): may reflect the signal, creating a "Faraday cage" effect.
• 💧 Water: Aquariums, heating pipes, and even people in the room absorb 2.4 GHz and 5 GHz frequencies.
• 📺 Household appliances: Microwaves and running motors create electromagnetic interference.

The frequency range is also critical. Signal 2.4 GHz It's better at avoiding obstacles and passing through walls, but it's heavily interfered with by neighboring networks. Range 5 GHz Provides high speed, but fades very quickly when encountering obstacles.

The router's location is crucial. If it's in a recess, behind a TV, or on the floor, the signal will be blocked by furniture and appliances. The ideal location is the center of the apartment, high up, with a direct line of sight to the main living areas.

Why does the internet work worse in the evening?

In the evening, from 7:00 PM to 11:00 PM, the airwaves experience peak load. Hundreds of routers in an apartment building operate on the same channels, creating a welter of interference. It's harder for your device to penetrate this noise, so the signal strength (SNR) drops, even if the transmitter's power remains constant.

Ways to improve reception and signal amplification

If measurements show values ​​worse than -75 dBm in work areas, the situation needs to be addressed. There are several proven methods, ranging from free to costly.

The first step is to optimize your router settings. Try switching to a less congested channel (especially for 2.4 GHz). It's also a good idea to separate the 2.4 and 5 GHz networks by giving them different names to force devices that require faster speeds to connect to the faster band.

If relocating the router doesn't help, consider hardware network expansion. Simple repeaters often cut speeds in half because they operate in half-duplex mode.

• 🔄 Mesh systems: A set of multiple modules that create a single, seamless network. The best solution for large apartments.
• 🔌 Powerline adapters: transmit the Internet through electrical wiring, allowing you to create a new access point in any outlet.
• 📡 External antennas: If your router supports replacing them, installing antennas with a higher gain (dBi) may improve the situation.

In some cases, updating the network adapter drivers on your computer or reflashing the router itself to alternative firmware (for example, OpenWrt), which allow you to fine-tune the transmitter power.

⚠️ Caution: Increasing the transmitter power (Tx Power) in your router settings above the factory default may cause the device to overheat and become unstable. Furthermore, this may violate radiation regulations.

Common mistakes when setting up a network

When trying to improve the signal, users often make common mistakes that only worsen the situation. One such mistake is installing too many amplifiers without proper configuration.

Another mistake is ignoring security standards. Using an outdated encryption protocol. WEP or WPA/TKIP Limits WiFi speed to 54 Mbps, regardless of signal strength. Always use WPA2/WPA3 with encryption AES.

Also, don't forget about noise from nearby devices. Bluetooth headsets, wireless mice, and baby monitors operate at the 2.4 GHz frequency and can create localized interference, reducing effective channel throughput.

Understanding the nature of a radio signal allows you to take systematic action rather than guesswork. By measuring the signal strength and removing physical obstacles or adjusting your equipment, you can get the most out of your internet connection.

What does -90 dBm mean?

A value of -90 dBm or lower is considered critical. At this level, the connection is extremely unstable, data packets are lost, and the device may constantly reconnect. This is essentially the limit of the router's audible range.

Does weather affect WiFi signal strength?

Indoors, the weather's impact is minimal. However, heavy rain, snow, or thunderstorms can weaken the signal if it comes from the provider over the air (radio, 4G/5G modem) or if the router is located near a window through which the signal passes.

Can foil on walls improve signal?

Foil acts as a shield. If you place it behind the router, it will reflect the signal in the desired direction (into the room), preventing it from escaping to neighbors or the street. However, if you wrap the receiving device itself in foil, the signal will be lost.

Why is the signal on 5 GHz weaker than on 2.4 GHz?

5 GHz waves are shorter, have poorer obstruction-bypass capabilities, and attenuate more quickly in space and wall materials. However, they are less congested and provide much higher data transfer rates.