When the internet is slow or, conversely, completely frozen, the first thing we look at is the bars in the corner of our smartphone screen. These familiar divisions create the illusion of simplicity, but they conceal a complex physical reality. In reality, Wi-Fi signal strength — this is not an abstract picture, but a precise physical quantity that can be measured and analyzed.
Understanding that, what is it measured in? Wireless network power gives users a huge advantage when setting up their home or office space. You stop wondering why the router has worse reception in the bedroom than in the kitchen and start using facts. The numbers will tell you the truth that interface designers have hidden.
The main unit you will encounter is dBm (decibel milliwatt). This is a logarithmic unit of measurement, often confusing beginners due to its negative values. The closer the number is to zero, the stronger the signal, and this is a fundamental rule to remember.
Physical basis: decibels and milliwatts
Radio signal strength is the energy transmitted by a router's antenna. However, this strength decreases due to attenuation in the air and obstacles (walls, furniture). For the convenience of engineers and users, a logarithmic scale was used, allowing for compact recording of vast ranges of values.
Meaning dBm Shows the ratio of signal strength to 1 milliwatt. Since Wi-Fi almost always deals with power less than 1 mW, the values are always negative. For example, -30 dBm is a very strong signal (almost right at the router), while -90 dBm means almost complete loss of connection.
It's important to distinguish between absolute power and receiver sensitivity. A router may "shout" loudly (high transmit power), but if your laptop has a low antenna sensitivity, it simply won't hear that "shout." reception level is often more important than the level of transmission.
⚠️ Attention: Don't confuse dBm (power) with dBi (antenna gain). dBi is a characteristic of the antenna itself, indicating how much it amplifies the signal compared to a theoretical emitter. A high dBi doesn't always mean a better signal in an apartment, as it can narrow the antenna's radiation pattern.
The logarithmic nature of the scale means that a 3 dBm change doubles or halves the actual signal strength. The difference between -50 dBm and -53 dBm seems small, but the signal is physically half as strong in the latter case. This is why jumps of 5-10 dBm can dramatically affect connection quality.
Interpretation of meanings: from ideal to dead zone
To effectively manage your network, it's essential to clearly understand which values are considered normal and which require intervention. The range of values is wide, and each range dictates its own internet usage conditions.
Here's a detailed breakdown of signal levels that every home network administrator should be familiar with:
- 🟢 -30 ... -50 dBm: Ideal signal. You're in close proximity to the router. The speed will be the maximum supported by your plan and equipment.
- 🟡 -50 ... -65 dBm: Excellent performance. Comfortable with 4K video, online gaming, and video conferencing. Standard for most residential environments.
- 🟠 -65 ... -75 dBm: Good/Average signal. Web browsing and email work without problems, but lag may occur with heavy gaming or buffering at high bitrates.
- 🔴 -75 ... -85 dBm: Weak signal. There's a connection, but the speed is slow. Drops and high ping are possible. Only suitable for instant messaging and texting.
- ⚫ -85 ... -90+ dBm: Dead zone. The device may show network availability, but fail to connect, or the connection will constantly drop out.
It's worth noting that different operating systems display this data differently. Android And Windows may show different "stick" patterns at the same dBm level due to different drivers and conversion algorithms.
Percentages vs. Decibels: The Eternal Confusion
Users often ask, "What's that in percentage?" Indeed, a scale from 0% to 100% seems clearer than negative decibels. However, there's no direct linear relationship, and different equipment manufacturers use different conversion formulas.
Most commonly, a nonlinear scale is encountered, where, for example, -50 dBm can be 100%, while -80 dBm is 0%. This creates a false sense of safety. You might see 40% of the signal, which seems like "almost half," but physically, this is already the unstable zone.
Below is a rough conversion table to help you navigate if your gadget doesn't display the exact numbers:
| Level (dBm) | Approximate % | Sticks (Android) | Connection quality |
|---|---|---|---|
| -30 ... -50 | 86% - 100% | 5/5 | Excellent |
| -51 ... -60 | 76% - 85% | 4/5 | Very good |
| -61 ... -70 | 56% - 75% | 3/5 | Good |
| -71 ... -80 | 26% - 55% | 2/5 | Low |
| -81 ... -90 | 0% - 25% | 1/5 | Critical |
That's why professionals never rely on "eyeballing" stripes. For accurate diagnostics, always use specialized utilities that display raw data.
Why do percentages lie?
Smartphone manufacturers often artificially lower the sensitivity of the signal level so that the user sees the "full signal" sooner and feels more comfortable, even if the actual signal strength is still far from ideal.
How to Measure a Signal: Tools and Utilities
To obtain accurate data, the operating system's built-in tools are often insufficient. You'll need specialized analysis applications that can read data directly from the Wi-Fi module.
On smartphones running Android the app is considered the market leader WiFi Analyzer (or its open-source counterparts, as the original app frequently changes owners and functionality). It displays a real-time graph, allowing you to walk around your apartment and see how the signal strength changes.
For users Windows There is a built-in, but hidden, command that produces a very detailed report. Open the command prompt (cmd) and enter:
netsh wlan show interfacesIn the list that appears, find the line "Signal." It will indicate the percentage, but in professional scanners, such as Acrylic Wi-Fi Home or inSSIDer, you will see exactly dBm.
⚠️ Attention: On devices iOS (iPhone, iPad) Apple restricts app access to raw Wi-Fi data for security reasons. You won't be able to see accurate dBm readings with third-party apps from the App Store without jailbreaking. Use Airport mode in macOS or third-party analyzers on Android for testing.
When taking measurements, hold the device in the same hand and position as you normally use it. The human body, which is mostly water, also absorbs radio waves and can introduce an error in measurements of up to 5-10 dBm.
Factors Affecting Signal Attenuation
Knowing, what is it measured in? signal, it's important to understand what exactly is causing these numbers to drop. The physics of radio wave propagation dictates its own conditions, and they cannot be ignored.
The first and foremost enemy is obstacles. Different materials affect 2.4 GHz and 5 GHz radio waves differently. Wooden partitions are almost transparent to the signal, while concrete walls with rebar can completely block the connection.
The second factor is interference. In apartment buildings, the airwaves are clogged with dozens of neighboring routers. If your channel overlaps with your neighbor's, a "mess" occurs, and the effective speed drops, even if the signal strength (dBm) is high.
- 🧱 Walls: Brick and concrete significantly attenuate the signal, especially at 5 GHz. Metal structures (rebar, insulation foil) act as a shield.
- 📺 Household appliances: Microwave ovens operating at 2.4 GHz create significant interference. Bluetooth devices also operate in this range.
- 💧 Water: Aquariums, heating pipes, and even indoor plants with large leaves can significantly weaken the signal.
☑️ Checking attenuation factors
Optimization: How to improve dBm performance
If measurements show unsatisfactory results (below -75 dBm in working areas), action is necessary. Simply increasing the transmitter power in the router settings is often ineffective, as the client device (phone) will still be unable to "shout" back to the router.
The first step should be proper router placement. Elevate it and keep it away from metal objects and mirrors. Sometimes, moving the device 50 centimeters to the side can increase signal strength by 3-5 dBm, which is significant.
If rearranging doesn't help, consider network expansion options:
- Wi-Fi repeaters: A simple, but not always effective, solution. They cut the speed in half, but can boost the signal strength in the far room.
- Mesh systems: A modern standard. Multiple modules create a single seamless network, automatically switching clients to the nearest point with the best signal.
- Powerline adapters: Internet is transmitted through regular electrical wiring. This is ideal if the walls are too thick to support radio waves, but there are outlets in every room.
⚠️ Attention: When setting up mesh systems or repeaters, it's important to choose the right location for the main node. If you place it in an area where the signal from the main router is already weak (-70 dBm), it will also transmit a weak signal. "Garbage in, garbage out."
Troubleshooting: When dBm Isn't Important
There are situations when the signal level is excellent (-40 dBm), but the internet is slow or lossy. In this case, the problem is not the power, but SNR (Signal-to-Noise Ratio) — signal-to-noise ratio.
If there's a lot of noise in the air (from neighboring networks, Bluetooth headsets, or wireless cameras), the desired signal is drowned out by interference. High dBm with low SNR means you're shouting loudly into the other person's ears, but there's loud music playing all around them, and they still can't understand you.
To resolve these issues, use a broadcast analyzer to find a clear channel. Switching from the congested 2.4 GHz band to the clearer 5 GHz band often resolves the issue even without improving signal strength.
What is interference?
This is the phenomenon of the superposition of two or more radio waves, which leads to a strengthening or weakening of the resulting signal. In Wi-Fi, destructive interference is most common, degrading the connection.
Why does my phone have 4 bars but the internet doesn't work?
The number of "bars" only indicates the received signal strength (RSSI), not its quality. If the channel is very noisy or the ISP is throttling the speed, the indicator will be full, but there will be no data. It's also possible that the router can hear the phone well, but the phone can't hear the router (channel asymmetry issue).
Can foil boost Wi-Fi signal?
In theory, foil can act as a reflector, directing the signal in a specific direction. However, in practice, creating an effective antenna from foil is difficult. More often than not, it simply shields the signal, creating dead zones behind it, or causes interference, worsening the situation.