Signal strength is how strong the radio signal from a mobile tower is at your device. It's most precisely measured in dBm (decibel-milliwatts), a negative number where closer to zero means stronger.
What the numbers mean
- -70 dBm or better: Excellent — full bars, fast data
- -85 to -70 dBm: Good — 4-5 bars, usable speed
- -100 to -85 dBm: Fair — 2-3 bars, slower
- -110 to -100 dBm: Weak — 1 bar, calls only
- Below -110 dBm: Effectively no signal
How to check your dBm
- iPhone: dial
*3001#12345#*for Field Test Mode - Android: Settings → About Phone → SIM Status → Signal Strength
The bars/dots on your status bar are a rough abstraction over the actual dBm reading — and different phones map them differently.
Why it matters
On a multi-network plan like Fuse, your phone reads dBm from all available networks and picks the strongest. On a single-network plan, you're stuck with whatever that one network is delivering.
See also
How Signal Strength (dBm) matters when picking a UK mobile plan
Understanding Signal Strength (dBm) helps you compare mobile providers on a like-for-like basis. Most consumer mobile pricing pages skip the technical detail — knowing the terminology means you can spot when a plan is genuinely better and when it just sounds that way. The Fuse Mobile glossary keeps definitions short and consumer-focused, no jargon-on-jargon.
Fuse Mobile is a UK multi-network data-only eSIM — it gives your phone access to all four UK mobile networks (EE, Three, Vodafone, O2) through a single profile. Where Signal Strength (dBm) is relevant to that setup, it's surfaced explicitly: pricing pages show real numbers, the coverage checker shows live per-network signal, and there's no hidden fee structure. See the plans page for the current pricing or read the multi-network eSIM explainer for the technical detail.