Why Is My Cell Signal Bad Inside My House?

Outside Is Fine, Inside Is Not

Cellular signals are radio waves, and radio waves lose energy every time they pass through a solid material. Standing in the driveway, your phone hears the tower almost directly. In the back bedroom, the same signal has crossed an exterior wall or a window, maybe a roof, and one or two interior walls first. Each layer takes a share, and the shares add up.

Signal strength is measured in dBm, and every 10 dB of loss cuts the signal's power to a tenth. A home that costs 30 dB between the curb and the couch delivers a thousandth of the power the phone saw outside. That is why a phone can show a strong signal on the porch and drop calls in the kitchen.

What in Your House Blocks Signal

Some materials barely matter. Others block most of the signal on their own.

The combinations are what hurt. A newer stucco house with Low-E windows can lose more through its shell than an older brick house with plain glass, which is why two homes on the same street, on the same carrier, can get completely different service.

Why 5G Can Be Worse Indoors Than LTE

Lower frequencies get through walls better than higher ones. The 600–900 MHz low bands reach deepest indoors but carry the least capacity. The mid bands that carry most LTE and much of 5G, from about 1.7 GHz up through the 3.45–3.7 GHz C-band, lose another 5–10 dB through the same building. Millimeter-wave 5G barely gets indoors at all.

So a phone can show a 5G icon outside and slow to a crawl inside, or fall back to LTE in some rooms. The icon tells you which technology the phone is attached to, not how strong or clean that signal is.

Your Carrier Matters More Than Your Phone

AT&T, Verizon, and T-Mobile each run their own towers on their own bands, so one network can be solid in your house while another is unusable. Prepaid and cable-company plans run on one of those three networks, so their coverage indoors is the host network's coverage. A neighbor's experience only tells you something if they are on the same network.

How to Fix Weak Signal at Home, Cheapest First

1. Turn on Wi-Fi calling

If your home internet is decent, Wi-Fi calling sends calls and texts over Wi-Fi instead of the cellular network. All three national carriers support it on most current phones, it is free, and it is a switch in your phone's settings. The catch: it is only as good as your Wi-Fi in the rooms where you need it.

2. Find out where signal is good and bad

Signal varies from room to room and floor to floor. Upper floors and rooms facing the nearest tower usually do best, and basements and interior rooms worst. Measuring beats guessing; here is how to check your signal in dBm and what the numbers mean.

3. Ask your carrier about a network extender

Some carriers offer a network extender, a small device that connects to your home internet and creates a little coverage bubble for that carrier only. What is offered changes over time, so ask.

4. Consider a booster, if the signal outside is usable

A signal booster picks up the outdoor signal with an antenna, usually on the roof or an outside wall, and rebroadcasts it inside. It can only amplify signal that exists: if the reading where the outdoor antenna would go is also weak, a booster has nothing to work with. FCC rules require you to register a consumer booster with your carrier, and a badly installed one can interfere with the network. For how boosters compare with other options, see DAS vs. small cell vs. booster.

5. Compare carriers

If another network is strong in your house, switching may be the real fix. Check before you switch, for example with a friend's phone on that network, room by room.

Bigger Than a House

Offices, apartment buildings, hospitals, and warehouses follow the same physics at a larger scale, with concrete, steel, and glass curtain walls instead of drywall. Our guide to why signal drops indoors covers commercial buildings in depth.