What the Cell Signal Bars on Your Phone Really Mean. Have you ever seen four bars and tried to text or download, but you can't? Here's why.

We all know what the bars graphic on the home screen of our mobile phones is supposed to mean. It indicates signal strength, right? As in how strong the signal is that our phone is receiving right now.

And in a very general sense, that’s what the bars (or dots, depending on your phone model) do. They generally indicate the relative strength of the available signal.

The key word here is ‘relative.’

What I mean is this: if your mobile phone displays from one to five bars (dots) indicating signal strength, then a display of four bars indicates a stronger available signal than three bars, and three a stronger signal than two, etc.

You may even have had this experience – your phone shows four bars, but when you try to text or download you can’t do it because you have no service despite the four big bars you see.

The truth is, there are no standards for signal strength bars.

Each mobile phone manufacturer uses an algorithm they’ve developed to sense the strength level of available signal. And then they show you however many or few bars they choose.

Of course that means it’s impossible to compare signal strength bars between different phone models. My phone’s three bars may well represent a stronger signal than your phone’s four bars. But there’s no way to know that by viewing the respective bars graphics.

The only reliable way to determine how strong a signal is available for your phone is to take a reading in decibels, or dBm. Decibels are a standard unit of measure, so when you take a dBm reading you know the absolute strength of the available signal.

dBm is typically expressed as a negative number, -88 for example. The closer to zero the reading is, the stronger the cell phone signal. So for example, -79 dBm is a stronger signal than -88 dBm.

A reading of -50 is the strongest signal you will see. When a signal is weaker than -100 dBm, that’s a pretty weak signal. If the signal gets much weaker than that, you likely won’t have service.

I’ve previously posted instructions to find the signal strength on your Android phone and to find the signal strength on your iPhone. It’s the only way to know how strong your available cell signal really is.

Because the bars, they don’t mean much.

 - Hardik Pakhale