Live model · Wi-Fi
How Wi-Fi Signal Strength Actually Works
Wi-Fi weakens with distance and loses a fixed amount through every wall between you and the router: a few dB through drywall, tens through concrete, about twice as much at 5 GHz as at 2.4. Your phone picks the fastest speed the signal still supports, so speed falls in steps, and a room behind the wrong wall gets nothing.
A router's signal, wall by wall, then over the whole flat
- CH4 Router
- CH1 Bed
How to read the stage
The router sits in the kitchen corner on 5 GHz. The bed is 9.5 m away in a straight line, and open air alone would leave −46.4 dBm there, plenty. But the line crosses the bathroom's concrete, which takes 45 dB, then a brick wall, 8 more: −99.4 dBm, no connection at all. Over the whole flat, 70% gets a signal good enough for a video call and 30% gets nothing.
Walls cost more than distance
Free space costs 20 dB every time the distance grows tenfold, so ten meters of open air costs about as much as one concrete wall at 2.4 GHz. At 5 GHz the same wall takes twice as much. On the walk in the second stage, through drywall every 4 m, 5 GHz drops out at 12 m while 2.4 GHz still runs at 13 Mb/s 24 m out. On 2.4 GHz, the bed gets 39 Mb/s.
Walking away through walls, on both bands
- CH4 5 GHz, 80 MHz channel
- CH2 2.4 GHz, 20 MHz channel
Why speed drops in steps
Each Wi-Fi speed is a modulation and coding scheme with the weakest signal it's specified to work at. A strong signal carries more bits per symbol; a weaker one needs a simpler, slower scheme. On an 80 MHz 5 GHz channel, 390 Mb/s needs −51 dBm and the slowest, 29.3 Mb/s, works down to −76. Below that floor there's no connection, which is what a dead zone is.
Where to put the router
In the third stage the same router goes in four places. In the kitchen corner, where the cable comes in, 70% of the flat gets a good signal; in the middle of the hall, 93%. A router in the middle of the home keeps every room close with few walls in the way. With a mesh node in the bedroom, every placement covers at least 97%.
Four places to put the router
- CH4 Router
What the model leaves out
This is a multi-wall model: free-space loss plus a fixed loss per wall on the straight line, with wall losses from one set of measurements. Real signals also bounce, bend around doorways and fade with furniture and people, so measured maps are patchier. Phones and routers with several antennas and streams run faster than one stream here, and a mesh node's own link back to the router, which the model treats as perfect, shares the air.
Questions
- Should I use 2.4 GHz or 5 GHz Wi-Fi?
- Near the router, 5 GHz: its wider channels carry far more, 390 Mb/s against 65 on one stream here. Through several walls or far away, 2.4 GHz: it loses about half as much per wall, so it keeps a connection where 5 GHz has dropped out. Most routers offer both and let devices move between them.
- What signal strength is good for Wi-Fi?
- −67 dBm is a common minimum for video calls and streaming, −70 for email and browsing, and −80 for a basic connection. Signal is measured in dBm, decibels relative to a milliwatt, so it's negative indoors and every 10 dB is a factor of ten in power. Here, below −76 dBm on 5 GHz or −82 on 2.4, nothing connects.
- What materials block Wi-Fi the most?
- Heavy concrete, by far: about 23 dB at 2.4 GHz and 45 at 5 GHz in iBwave's measurements, against roughly 5 and 10 for a drywall partition. The CWNA study guide puts brick and concrete at 12 dB and an elevator or metal obstacle at 10 dB at 2.4 GHz, against 3 dB for drywall or plain glass.
- Do Wi-Fi extenders and mesh systems help?
- They put a second transmitter on the far side of the walls, so rooms behind concrete get a nearby source. In the third stage, a mesh node in the bedroom lifts every router placement to at least 97% of the flat covered well. The model gives the node a perfect link back to the router; a wireless node shares the air with your devices, so the real gain is smaller.