Have you ever noticed how your smartphone or laptop displays your Wi-Fi level as bars or percentages, while in your router settings, mysterious numbers like -65 dBm or 20 dBiWhy do manufacturers use different units of measurement, and which one is the most accurate? In this article, we'll explore how Wi-Fi signal strength is measured, which units are used in different devices, and what they mean in practice—from choosing a router location to diagnosing connection issues.
Spoiler: The percentage on your phone is not the actual signal strength., but only a subjective assessment of the device. And here decibel-milliwatts (dBm) is the only universal unit by which one can objectively compare the quality of the network at different points in the home.But there are nuances here too: for example, antennas are measured in dBi, and the data transfer rate is in MbpsLet's look at how these values are related and how to use them to optimize your Wi-Fi network.
1. Decibels-milliwatts (dBm) are the “golden” unit of measurement for Wi-Fi.
If you've ever looked into router settings or used Wi-Fi analysis programs (for example, WiFi Analyzer or NetSpot), then you probably saw values like -30 dBm or -80 dBmThis is the basic unit of measurement of signal strength - decibel-milliwatt (dBm).
dBm It shows how powerful the signal is reaching your device compared to the reference value of 1 milliwatt. The special thing about this unit is that it logarithmic: a change of 3 dBm means doubling or decreasing the power by a factor of 2, and a change of 10 dBm means decreasing the power by a factor of 10. For example:
- 📶 -30 dBm - excellent signal (maximum speed, stable connection).
- 📶 -50 dBm - good signal (minor speed loss is possible).
- 📶 -70 dBm - weak signal (interruptions and low speed are possible).
- 📶 -90 dBm — critical level (the network may not connect).
It is important to understand that dBm is always a negative number: the closer to zero (for example, -40 dBm), the better the signal. But -100 dBm — it's almost nonexistent. However, even a small change in dBm can greatly impact connection quality. For example, the difference between -65 dBm And -75 dBm - it's not 10 units, but 10 times reduction in power!
2. Percentages (%) - Why do they lie?
Smartphones, laptops, and even some routers often display Wi-Fi connection levels as percentages: "100%," "75%," "20%." It seems convenient! But here's the problem: percentages are not an objective measure of power, and a subjective assessment of the device, which depends on:
- 📱 Device models: one smartphone will show 80% at -70 dBm, and the other one is 50% with the same value.
- 📡 Wi-Fi module sensitivity: cheap adapters can "lie" more than professional ones.
- 🔄 Manufacturer's algorithm: some brands (eg Apple or Samsung) deliberately “inflate” the percentages for marketing purposes.
For example, on iPhone three "sticks" of the signal can correspond -65 dBm, and on Xiaomi — -80 dBm. That's why You can't rely on percentages when setting up a network — they are only good for rough estimates. If you need to accurately measure signal quality, use specialized applications (for example, WiFi Analyzer For Android or AirPort Utility For iOS), which show real values in dBm.
netsh wlan show interfacesIn the line Signal the level will be indicated in percentage and dBm (for example, 95% (-45 dBm)).-->
3. dBi – how is antenna power measured?
If dBm shows power received signal, then dBi (isotropic decibel) characterizes antenna gainThis unit indicates how much more efficiently an antenna radiates a signal compared to a hypothetical "isotropic radiator" (which distributes energy evenly in all directions).
For example:
- 📡 Antenna with 2 dBi — standard “rubber band” on most routers (weak gain, wide coverage angle).
- 📡 Antenna with 5 dBi - medium gain, suitable for apartments.
- 📡 Antenna with 9 dBi - narrow-focus, used for long-distance connections (for example, point-to-point between houses).
Important: Increasing dBi does not always mean a better signal. High gain antennas (eg 12 dBi) have narrow radiation pattern — they "shoot" a signal in one direction, but poorly cover adjacent rooms. Therefore, antennas are usually optimal for the home. 5–7 dBi.
| dBi | Antenna type | Example of use | Coverage angle (approximately) |
|---|---|---|---|
| 2–3 dBi | Built into the router | Small apartments | 360° (circular) |
| 5–7 dBi | Removable external | Apartments, small offices | 120–180° |
| 9–12 dBi | Directional (panel, sector) | Long-distance connections, street networks | 30–90° |
| 15+ dBi | Parabolic grid antenna | Communication for kilometers (point-to-point) | 5–20° |
4. Other units: mW, RSRP, SNR - what are they?
Besides dBm and dBi, you'll also find other Wi-Fi-related units of measurement in technical specifications. Let's take a look at what they mean:
- 🔋 mW (milliwatts): a direct measure of signal strength (1 mW = 0 dBm). For example, 100 mW = 20 dBm. It is rarely used, since dBm is more convenient for logarithmic calculations.
- 📊 RSRP (Reference Signal Received Power): used in 4G/5G, but is sometimes mentioned in the context of Wi-Fi 6/6E. It shows the reference signal strength (similar to dBm, but for mobile networks).
- 🔇 SNR (Signal-to-Noise Ratio): signal to noise ratio, measured in dB. A good value is 25+ dB, bad - <10 dB. SNR is more important than dBm: even with a weak signal (-80 dBm) high SNR (e.g. 30 dB) will ensure a stable connection.
- 📡 Tx Power (transmission power): measured in dBm or mW, it shows how loud the router is. The maximum value depends on the Wi-Fi standard and legislation (for example, in EU limitation - 20 dBm (100 mW)).
In practice, the most important thing for Wi-Fi diagnostics is dBm And SNRFor example, if your laptop shows -70 dBm at SNR 15 dB, the problem may not be in the weak signal, but in interference (Neighboring networks, microwave ovens, Bluetooth devices). In this case, changing the channel in the router settings will help.
How to check SNR on Windows?
Open Command line and enter:
netsh wlan show interfacesIn the line Signal the value will be indicated SNR (if supported by the driver).
5. How to measure Wi-Fi signal: tools and methods
To objectively assess the quality of Wi-Fi in your home, it is not enough to look at the “sticks” on your phone. Here 3 reliable ways measure signal:
- Mobile applications:
- 📱 WiFi Analyzer (Android) - shows dBm, channels, load.
- 📱 AirPort Utility (iOS) - hidden function (you need to hold your finger on the Wi-Fi graph).
- 📱 NetSpot (Windows/macOS) — creates a heat map of the signal.
- Built-in OS tools:
- 🖥️
netsh wlan show interfaces(Windows). - 🍎 Hold
Option (Alt)+ click on the Wi-Fi icon (macOS).
- 🖥️
- 📡 Wi-Fi analyzers (For example, Fluke Networks AirCheck).
- 📡 Spectrum analyzer (to search for interference).
There are plenty of free apps for home use. The main thing is check the signal at several points (near the router, in the far corner, on different floors). If the difference between the maximum and minimum dBm values exceeds 20–30 dBm, it is worth thinking about strengthening the network (repeater, Mesh system, replacing antennas).
Check the dBm level in different rooms | Compare SNR (should be >15 dB) | Change the channel in the router settings | Update the router firmware | Check for interference (microwaves, other networks) -->
6. How to improve the signal: practical tips
Knowing what Wi-Fi is measured in can help you improve your coverage in a targeted manner. Here's 5 working methods:
- 📍 Positioning the routerPlace it in the center of the house, 1–2 meters high (not in a closet!). Avoid concrete or metal walls.
- 🔄 Changing the channel: in the router settings (
Wireless → Channel) select the least loaded channel (use WiFi Analyzer for analysis). - 📶 Replacing antennas: If your router has removable antennas, install models with 5–7 dBi (For example, TP-Link TL-ANT2405CL).
- 🔗 Mesh system or repeater: if the house is large, add nodes Google Nest WiFi or TP-Link Deco.
- 🔧 Firmware update: Older versions of router software may limit transmission power.
Please note: If your router supports Wi-Fi 6 (802.11ax), it can automatically optimize the signal using technology OFDMA And BSS ColoringHowever, even with Wi-Fi 6, it's important to monitor dBm levels—new standards don't change the laws of physics!
7. Common Mistakes When Measuring Wi-Fi
Many users make mistakes that distort the measurement results. Here's what you can't do it:
- 🚫 Check the signal at one point only: dBm can vary greatly even just a meter away from the router.
- 🚫 Ignore interference: Neighboring networks on the same channel can "clog" your signal, even if the dBm is high.
- 🚫 Compare dBm of different devices: a smartphone and a laptop can show different values with the same signal.
- 🚫 Relying on "sticks": as we have found out, percentages are not an objective measure.
Another common mistake is do not take into account Wi-Fi standards. For example, Wi-Fi 6 (802.11ax) may show lower dBm than Wi-Fi 5 (802.11ac), but at the same time provide a more stable connection due to better signal processing. Therefore, when optimizing your network, focus not only on dBm, but also on real speed (measured through Speedtest) And connection stability.
⚠️ Attention: The maximum permitted Wi-Fi transmit power (Tx Power) is regulated by local laws. For example, in Europe And Russia for 2.4 GHz the limitation is - 20 dBm (100 mW), and in USA — 30 dBm (1 W)Exceeding the limit may result in interference with other devices and fines. Check current regulations for your region.
FAQ: Answers to Frequently Asked Questions
🔍 Why does my phone have 3 Wi-Fi bars, but the speed is slow?
The sticks show signal level (dBm), but do not take into account interference (SNR) and network congestionPossible reasons:
- Too many devices are connected to the router.
- Neighboring networks operate on the same channel.
- The router is overloaded (for example, torrents are being downloaded).
Solution: Change the channel in your router settings, limit the number of connected devices, or update the firmware.
📶 What is the minimum dBm value required for stable Wi-Fi?
It depends on the Wi-Fi standard and tasks:
- -65 dBm and above: great for 4K streaming and online games.
- -70 dBm: enough for web surfing And social networks.
- -75 dBm and below: possible breaks, low speed.
At the same time SNR should be at least 15 dB.
🔄 Which Wi-Fi channel should I choose for maximum signal?
In the range 2.4 GHz (the longest range, but overloaded) it is better to choose channels 1, 6 or 11 - they do not intersect. 5 GHz There are more channels, but they penetrate walls worse. Use the app WiFi Analyzerto find the clearest channel in your area.
📡 Is it possible to increase dBm using software?
No, dBm is a physical quantity, it cannot be changed programmatically. However, it is possible:
- Increase
Tx Powerin the router settings (if supported). - Use antennas with a large dBi.
- Install a repeater or mesh system.
Caution: Increase Tx Power may violate local regulations and create a nuisance to neighbors.
🛠️ Why didn't the signal improve after replacing the antenna?
Possible reasons:
- High gain antenna dBi (For example, 9 dBi) has a narrow beam pattern - it may be shining past your devices.
- Poor connector contact (check if the antenna is screwed in tightly).
- The router does not support external antennas (in some models the connectors are blocked).
Solution: Try an antenna with 5–7 dBi and check the coverage at different points.