RSSI stands for Received Signal Strength Indicator, and it tells you how strong a WiFi signal is when it reaches your device. It’s measured in decibels relative to a milliwatt (dBm), on a scale that runs from 0 (strongest possible) to -100 (no usable signal). If you’ve ever wondered why your laptop streams perfectly in the living room but buffers in the bedroom, RSSI is the number that explains it.
How the dBm Scale Works
The dBm scale is negative and logarithmic, which makes it a little counterintuitive at first. A value of -30 dBm is an extremely strong signal, while -80 dBm is barely functional. The key thing to remember: the closer the number is to zero, the better your connection.
Because the scale is logarithmic, small numerical changes represent big real-world differences. Every 6 dBm change in RSSI roughly doubles or halves the effective distance between your device and the router. So dropping from -50 to -56 dBm isn’t a tiny dip. It’s equivalent to being twice as far away.
Signal Strength Ranges
Here’s what different RSSI values mean in practice:
- -30 to -50 dBm (Excellent): The strongest signal you’ll realistically see. Suitable for anything, including 4K streaming, video calls, and online gaming.
- -50 to -65 dBm (Very good): Still strong enough for streaming video, voice calls over WiFi, and smooth performance on phones and tablets.
- -65 to -70 dBm (Acceptable): Good enough for web browsing, email, and lighter tasks. You can still stream video, but you may notice occasional hiccups.
- -70 to -80 dBm (Poor): Basic connectivity works, but packet delivery becomes unreliable. Downloads stall, video buffers, and video calls break up.
- -80 to -90 dBm (Very poor): Mostly noise at this point. Your device might show a connection, but it won’t do much useful with it.
- -90 to -100 dBm (Unusable): Effectively no signal.
A practical rule of thumb: if your RSSI is worse than -70 dBm, you’re unlikely to have good performance for anything bandwidth-intensive.
What Weakens Your Signal
Distance is the obvious factor. In open space, WiFi signals weaken by about 0.02 dB per foot. But walls and furniture do far more damage than air does. Glass and wood absorb 2 to 5 dB. Plasterboard costs you 3 to 5 dB. Brick walls knock off 8 to 12 dB. And concrete or metal surfaces, like a basement floor or a refrigerator, can strip away 10 to 15 dB or more. Two concrete walls between you and your router could easily push a strong -45 dBm signal down to a marginal -70.
Your frequency band matters too. The 2.4 GHz band travels farther and penetrates walls better, but it’s crowded with interference from other devices like microwaves and Bluetooth speakers. The 5 GHz band offers faster speeds and less congestion, but its shorter wavelength means it weakens more quickly over distance and struggles more with obstacles.
RSSI vs. Signal-to-Noise Ratio
RSSI tells you how loud the signal is. Signal-to-Noise Ratio (SNR) tells you how much louder the signal is compared to background noise. Both matter, but they measure different things. You could have a decent RSSI of -60 dBm and still have connection problems if the noise floor in your environment is unusually high, perhaps from neighboring networks or electronic interference. In that scenario, the SNR would be low even though the raw signal strength looks fine.
Think of it like trying to hear someone at a party. RSSI is how loudly they’re speaking. SNR is how loudly they’re speaking relative to the crowd noise. A whisper in a quiet room can be easier to understand than shouting in a nightclub.
How RSSI Affects Your Speed
Your router doesn’t always transmit data at the same rate. It constantly adjusts its encoding method based on signal conditions. When RSSI is strong, the router uses more complex encoding that packs more data into each transmission. As the signal weakens, it shifts to simpler, slower methods to keep the connection from dropping entirely.
For example, on an 80 MHz channel with two data streams, an RSSI of -58 dBm can support roughly 400 Mbps. Drop to -60 dBm and the available rate falls to around 351 Mbps. At -64 dBm, the router steps down another level. These shifts happen automatically and invisibly, which is why your internet can feel slower in one room even though your device still shows a WiFi connection.
Why RSSI Values Vary Between Devices
One quirk worth knowing: RSSI isn’t perfectly standardized. The WiFi protocol (IEEE 802.11) defines RSSI as a value between 0 and 255 that increases with signal energy, but it doesn’t specify exactly how manufacturers should calculate it. Each chipmaker, whether Intel, Qualcomm, or Broadcom, implements RSSI generation with its own algorithm. That’s why your phone and laptop might report slightly different RSSI values while sitting in the same spot. The dBm values are generally comparable across devices, but small discrepancies of a few dB are normal.
How to Check Your RSSI
On a Mac, hold the Option key and click the WiFi icon in the menu bar. You’ll see RSSI listed alongside other connection details. On Windows, open a command prompt and type netsh wlan show interfaces, then look for the “Signal” line (shown as a percentage) or use a free tool like WiFi Analyzer to see dBm values directly. On Android, WiFi Analyzer apps show real-time dBm readings. On iPhones, Apple doesn’t expose RSSI in a user-friendly way, but the number of signal bars gives a rough approximation.
Improving a Weak Signal
If your RSSI is consistently below -70 dBm where you need it, a few physical adjustments can help before you spend money on new hardware.
Router placement makes a surprising difference. Placing your router on a table or shelf about 1 to 1.5 feet high, so the antenna sits on roughly the same horizontal plane as your devices, maximizes the reach of its omnidirectional antennas. Keeping the router elevated rather than on the floor can improve signal strength by 10 dB or more in some setups.
Antenna angle matters too. TP-Link testing showed that tilting a router’s antenna forward at 45 degrees produced a signal of -26 dBm near the router, while laying it completely horizontal dropped the reading to -39 dBm. For single-floor coverage, keeping antennas vertical is generally best. If you need to cover multiple floors, angling one antenna vertically and one at 45 degrees helps spread the signal both horizontally and vertically.
Beyond positioning, reducing the number of walls between your router and your device is the single most effective change. Moving the router from a back closet to a central room can shift your RSSI from poor to very good without any equipment upgrades. If that’s not possible, a mesh network system or a wired access point in the weak zone will solve the problem more reliably than range extenders, which often introduce their own signal loss.