Wi-Fi signal strength: what it's measured in and how to interpret the readings correctly

When it comes to setting up a home or office Wi-Fi network, one of the key parameters is signal strengthBut few people know the numbers behind the indicators on their smartphones or in network analysis programs. Why do some apps show the signal in dBm, in others - in percent, and in the router settings you can find mWUnderstanding these units is important not only for diagnosing problems, but also for properly placing equipment and selecting antennas or amplifiers.

In this article we will examine in detail:

• 🔹 Basic units of measurement Wi-Fi power (dBm, mW, %) and how they relate to each other.
• 🔹 Why percentages on devices — this is a conditional value, not an exact metric.
• 🔹 How practically apply this knowledge to improve network coverage.
• 🔹 Common mistakes when interpreting indicators and how to avoid them.

If you've ever wondered why your smartphone shows "100% signal" near a router, but your internet speed leaves much to be desired, the answer lies in understanding units of measurement. Let's take a look.

1. dBm is the basic unit of measurement for Wi-Fi power.

dBm (decibel-milliwatt) — is a logarithmic unit that shows relative signal strength compared to 1 mW. It is used by professionals because it conveniently reflects both very weak and strong signals in a compact range of numbers (usually from -100 dBm to 0 dBm).

Key Features dBm:

• 📉 Negative values - this is the norm: -30 dBm (very strong signal) better than -80 dBm (weak).
• 🔄 Logarithmic scale: increase by 3 dBm means doubling the power, and decreasing it by 3 dBm — halved.
• 🌍 Versatility: used in all Wi-Fi standards (802.11a/b/g/n/ac/ax).

Example: If your laptop shows -67 dBm, and the smartphone is nearby - -75 dBm, this means that the laptop is receiving a signal 4 times more powerful (difference in 8 dBm ≈ 2³).

2. mW (milliwatts) is the absolute power of the transmitter.

mW (milliwatts) is absolute physical quantity, showing the actual radiated power of the antenna. Router specifications often indicate the transmitter power in mW (For example, 100 mW or 200 mW). However, in practice, to measure the signal level mW They are rarely used due to the inconvenience of working with large ranges of values ​​(from fractions of μW to hundreds of mW).

The connection between dBm And mW is described by the formula:

dBm = 10 × log₁₀(mW)

For example, power 100 mW equal 20 dBm, A 1 mW - This 0 dBm (reference point).

Important: in Russia and the EU, the maximum permitted power for Wi-Fi in the 2.4 GHz range is 100 mW (20 dBm), and in 5 GHz – up to 200 mW (23 dBm), depending on the channel. Exceeding these values ​​may result in interference with other devices and fines from regulators.

3. Percentages (%) - subjective assessment of devices

When your smartphone or laptop shows "Wi-Fi signal: 75%", it not an accurate power metric, A subjective assessment, which the device calculates independently. Conversion algorithms dBm Each manufacturer has its own percentage, therefore:

• 📱 iPhone can show 100% at -50 dBm,
• 🤖 Android-devices - when -30 dBm,
• 💻 Windows often uses a non-linear scale.

Example: at the same distance from the router:

• 🍎 iPhone 13 will show 80%,
• 🤖 Samsung Galaxy S22 — 65%,
• 🖥️ Laptop with Windows 11 — 90%.

This creates confusion, so for accurate diagnosis it is always better to use specialized applications (for example, WiFi Analyzer or NetSpot), which show the signal in dBm.

Percentages (0-100%)|dBm (e.g. -67)|Number of "bars" (1-4)|I don't know, I didn't pay attention-->

4. Other units: dBi, RSSI, SNR - what are they?

In addition to signal strength, Wi-Fi settings also contain other units:

• 📡 dBi — antenna gain. Shows how much the antenna focuses the signal compared to an isotropic radiator. For example, an antenna 5 dBi amplifies the signal by 3.16 times compared to 2 dBi.
• 📶 RSSI (Received Signal Strength Indicator) - This raw signal strength indicator, which is then converted into dBm or percentages. RSSI typically varies from 0 (weak) to 255 (strong), but the scale depends on the Wi-Fi chip.
• 🔊 SNR (Signal-to-Noise Ratio) — signal to noise ratio, measured in dB. Good value: > 25 dBIf the SNR is low (e.g. 10 dB), even with a high signal level, the connection will be unstable.

Example: If your router has antennas 5 dBi, and the neighboring one is 2 dBi, this does not mean that its signal is 2.5 times stronger. Antenna gain works in both directions: it “hears” devices better, but also emits more focused sound.

5. How to measure Wi-Fi signal strength?

For accurate diagnosis, use the following methods:

1. Specialized applications:
   • 📱 WiFi Analyzer (Android) - shows signals of all networks in dBm.
   • 🍎 AirPort Utility (iOS) is a built-in tool for Apple devices.
   • 💻 NetSpot or inSSIDer (Windows/macOS) - Professional tools with coverage visualization.

Name: Wi-Fi
Description : Intel(R) Wi-Fi 6 AX200
Status: connected
SSID                : MyHomeWiFi
Speed: 866 Mbps
Signal: 85%
...