Measurements
Bars Are Convenient. Measurements Are Better.
Signal bars answer a casual question: is the link roughly strong or roughly weak? dBm answers a sharper one: how much power is the phone measuring? The two are related, and they are not the same display.
What the bars leave out
A bar table is chosen by the device maker. One phone may still show several bars at a reading where another has already dropped a bar. Bars also hide small changes. A move from −84 dBm to −96 dBm can be one bar or none, depending on the table, and that move can be the difference between a comfortable indoor link and a fragile one.
How to read dBm
The number is negative. −70 dBm is stronger than −100 dBm. A practical scale on the homepage groups common ranges from excellent to very weak. Treat the edges as approximate. Radios, antennas, and networks do not share one universal cutoff.
Why a strong number can still feel slow
dBm describes the link, not the queue. Latency and congestion can make pages wait while the power reading stays healthy. If you compare places, compare the same phone, and note the time of day next to the number.
- Signal bars
- A coarse icon. Good for noticing a drop. Poor for comparing two devices.
- dBm
- Received power. Closer to zero is stronger.
- Latency
- Waiting time before data starts to move.
- Network congestion
- Demand on the site you are using.
- Indoor attenuation
- Extra loss from the building around you.