How do I check mobile coverage before switching network?

Coverage maps are modelled, not measured. They are useful for ruling networks out and hopeless at predicting what happens inside a house with thick walls or foil-backed insulation.

Step by step

1. Use Ofcom's checker rather than the networks' own maps.It covers all four UK networks in one place and is not a marketing tool. Check by full address, not postcode, because coverage varies within a postcode.
2. Read indoor and outdoor separately.The checker distinguishes them. Good outdoor and poor indoor is the commonest pattern, and it is the indoor figure that determines whether your phone rings in the kitchen.
3. Check the places you actually are.Home, work, the school, the relative you visit weekly, and the route between them. A network that is strong at home and absent at work is not a good fit.
4. Know that some networks share masts.Coverage from different brands can be identical because they use the same physical network. Switching brand without switching underlying network changes nothing about signal.
5. Test with a cheap SIM before moving.A pay-as-you-go SIM costs very little and gives a definitive answer in a week. This is the only genuinely reliable test.
6. Check whether wifi calling is supported.If indoor coverage is poor everywhere, wifi calling matters more than the coverage map. All four UK networks support it, but not on every tariff or handset.
7. Look at 4G as well as 5G.5G coverage is patchy outside towns and irrelevant if 4G is weak where you live. Solid 4G is more useful day to day than intermittent 5G.
8. Report persistent problems.If coverage is far worse than predicted at your address, tell the network. Some will supply a signal booster or confirm a fault; it also strengthens a case to leave without penalty.

Tips

• Ask neighbours which network they use and whether it works indoors. Local experience beats a coverage map.
• Foil-backed insulation, modern coated glass and thick stone all block mobile signal heavily — a new efficient house can have worse indoor signal than an old one.
• If you are on a monthly rolling contract, testing a new network costs nothing but a month.

Common mistakes

• Trusting the network's own coverage map — They are optimistic by design and usually show outdoor prediction by default, which is not the number that matters at home.
• Signing a long contract without testing — Coverage is the one thing you cannot fix afterwards, and a two-year contract with no signal at home is an expensive mistake.

If it doesn't work

Questions people ask