Wi-Fi Signal Strength Estimator

What does Wi-Fi signal strength (dBm) actually mean?

Wi-Fi signal strength is measured in dBm — decibel-milliwatts — a logarithmic scale that describes how much radio power your phone or laptop receives from the router. The numbers are always negative, and the golden rule is simple: the closer the number is to zero, the stronger the signal. So -40 dBm is much stronger than -75 dBm. Because the scale is logarithmic, every 10 dB difference represents a ten-fold change in received power; a drop from -50 to -60 dBm means your device is getting one tenth of the power it was getting before.

In practice, the signal you see on your device falls into a few familiar bands. Anything between -30 and -50 dBm is excellent: you are sitting right next to the router and everything from 4K streaming to online gaming feels instant. From -50 to -60 dBm is good: HD video, video calls and gaming all work comfortably. The -60 to -67 dBm range is fair: browsing and video calls are usually fine, but 4K streams can start buffering. Below -70 dBm the connection is weak — expect dropped calls and stuttering video — and once you slip past -80 dBm the network is barely usable, with connections dropping or failing to establish at all.

How this estimator works

This tool builds its estimate from three ingredients: distance, walls and frequency band. It starts from a reference signal of -30 dBm at 1 metre, roughly what a typical home router delivers right next to the device. Signal then falls with distance according to the free-space path loss rule: you lose about 6 dB every time the distance doubles, which the calculator expresses as 20 × log₁₀(distance in metres).

Walls come next. Each wall between you and the router subtracts a penalty based on its material: about 3 dB for drywall or wood, 6 dB for brick and 12 dB for concrete. Finally, the Wi-Fi band matters: a 5 GHz signal is absorbed faster by air and obstacles, so the model subtracts roughly 6 dB relative to 2.4 GHz, which travels further but at lower top speeds. The calculator adds all three losses to the -30 dBm reference and rounds to one decimal place.

Worked example

Say your router is 5 metres away, behind one drywall, and you are connected on the 2.4 GHz band. The distance loss is 20 × log₁₀(5) ≈ 13.98 dB. Adding the drywall penalty of 3 dB gives a total loss of 16.98 dB, so the estimate is -30 − 13.98 − 3 = -47.0 dBm — an Excellent signal. Now imagine the same spot on 5 GHz, but the wall is brick (6 dB). That gives -30 − 13.98 − 6 − 6 = -59.0 dBm, still Good, but noticeably weaker — a fair preview of why the faster band sometimes feels worse a room or two away.

Practical tips to improve a weak signal

If your estimate lands in the Weak or Poor band, start with placement: put the router central and elevated — on a shelf rather than the floor, away from corners — so its signal reaches every room evenly. Try switching bands: if you are far from the router, the 2.4 GHz network will often reach where 5 GHz gives up. Note that concrete walls are the big killer; a single poured-concrete wall can cost you 12 dB, equivalent to quadrupling your distance. Keep the router away from metal obstructions like filing cabinets, fridges and mirrors, which reflect radio waves. If the router still cannot reach the far bedroom, a mesh node or Wi-Fi extender placed halfway will usually fix it — and for a desk that never moves, a cheap wired Ethernet connection beats every wireless trick.