Woman using phone with pink phone case

Do phone cases block signal?

We´ve all been there, you need to make an important call or send the boss a quick update over WhatsApp and, bang, your phone loses signal! This can be more than a little frustrating, especially when our beloved smartphones fail us at precisely the wrong moment!

But could that little phone case so innocently wrapped around your device be to blame?

Well, let´s find out!

Do phone cases block signal (quick summary) – most ´standard´ phone cases (TPU / polycarbonate / silicone) are radio transparent and DO NOT block signal. Metal cases, on the other hand, DO sometimes block radio waves and could potentially affect your phone´s signal.

What is signal and can it be ´blocked´?

When we talk on our cell phones, our voice is broken down into electrical signal and transmitted from the antenna within our devices (I´m sure you remember the good old days when cell phone antennas weren´t quite so discreet) to the nearest ´cell tower´ as radio waves. 

´Signal´ is basically a measure of how efficiently our phone is able to transmit radio waves from its antenna to your service provider´s nearest ´cell tower´ and vice versa.

Unfortunately, radio waves can be blocked by anything that isn´t radio transparent (anything that doesn´t allow them to pass through).

So, what blocks cell phone signal?

Well, actually, quite a lot of things! Here´s a quick rundown of the worst offenders –

Terrain / Thick vegetation – did you have signal the last time you were hiking through a forest or down in a valley? If the answer is no, then chances are that the thick forest canopy or surrounding hills were blocking those radio waves!

Extreme weather – adverse weather conditions, such as heavy rain, thunderstorms, gale force wind, etc., will also ´block´ your cell phone´s signal

Certain materials – according to Wilson Amplifiers, the U.S. market leaders in signal boosting technology, many different materials, including concrete, brick, metal (oh, oh!), glass, wood and plywood, can block signal to some degree or other!

Why do some phone cases block signal?

Well, phone cases form a ´barrier´ (albeit a thin one) between your phone´s antenna and the nearest cell tower. That being said, most bog-standard phone cases DO NOT affect your phone´s signal.

There are, though, certain materials (I´m looking at you metal) used in phone cases that CAN affect the strength of your phone´s signal. 

Here´s a quick overview for each type of material commonly used in phone cases –

TPU / Silicone

Cases made from plastic (TPU or polycarbonate) or silicone shouldn´t block or interfere with your phone´s signal. According to Scientific American, ´… thin amounts of plastic wrap … [or] rubber are not likely to interfere with radio waves.´

Basically, you´ve nothing to fear if you´ve wrapped your phone in a standard TPU or silicone Apple case!

Waterproof cases / Battery cases

We scoured Amazon for best-selling waterproof cases, and it turns out that the majority are made almost entirely of PVC (also used to make pipes!)

PVC is a form of plastic and DOESN´T block radio waves (breathes sigh of relief!)

Similarly, battery cases are normally made from either plastic or silicone (Apple´s signature ´Smart battery Case´ is made of silicone), so no problem there either!

Aluminium / Metal

So, it´s all been fine and dandy up until now, no cause for concern! But what about metal?

Well, metal can and does block radio waves … and don´t just take my word for it, the Encyclopedia Britannica has this to say – ´Radio waves … CANNOT pass through electrical conductors, such as water and metals. ´ Crikey!

Apple actually filed a patent back in 2015 for a new ´composite´ material that looks like metal but allows radio waves to pass through. They wanted to give the iPhone a sleek ´metallic´ look without negatively affecting signal strength …

Businessman frustrated due to lack of signal

But don´t start stripping that metal case from your phone just yet!

Whether or not a metal case blocks signal depends on a number of factors –

1. Type of metal – copper (thankfully VERY uncommon in phone cases) is the worst offender.

2. Quantity of metal used – obviously if there´s a little bit of aluminium strategically melded into certain areas of your case, it´s not going to be of as much concern as a case made solely from aluminum.

3. Whether or not the metal blocks your phone´s antenna. In Apple devices the ´main´ antenna is located INSIDE the device, tucked in just behind the charging port.


At the end of the day, it´s extremely difficult to know whether a phone case is going to block signal just by reading the product description. If you really want a metal phone case, I strongly advise that you make sure it has a good number of reviews AND that you read them thoroughly before making a purchase! 

How to find out if your case is blocking signal

If your phone has lost signal, the easiest way to figure out why is by testing each potential variable one by one.

First, consider your surroundings, if you´re outside and there´s thick foliage then that´s probably the issue (if you´re in a tunnel or there´s a raging storm outside, well, you probably already know what the problem is).

Second, try turning your device on and off.

Third, if anyone you´re with uses the same service provider, ask them to check their signal strength. Occasionally ´cell towers´ get overwhelmed, especially if there´s a sudden influx of people to a certain area!

If you think your case might be to blame, just take it off and check whether the signal is any stronger when your device is case-free.

If you want to know the exact extent to which a phone case is blocking your signal, you can run a test via the hidden Field Test app. This app is far more accurate (although, admittedly, a little more difficult to use) than the ´signal bars´ on your phone´s display.

To access the app, you need to type *3001#12345#* into your phone (as if you were making a call) and then press dial. This will automatically open Field Test on your device.

Once in the app hit ´LTE´ and then ´Serving Cell Measure´, you´ll then be greeted by some fluctuating data. It may look a little confusing, but don´t be put off! Just scan the data for the´rsrp0´ (´Reference Signal Received Power´) figure.

´Rsrp0´ ranges from about -55 to -145; the higher number, the stronger the signal!

Check the ´rsrp0´ figure both with and without a phone case and compare results.

Here´s a good YouTube tutorial on using the Field Test app –

Are there any phone cases on the market that actually boost signal?

Yes, actually, there are! There are two main types, those with ´antennas´ that extend from the case (normally from both top and bottom) and those that claim to ´amplify´ your phone´s signal. The jury´s still out as to whether they´re effective!

There are also several signal boosting devices on the market for home / vehicle use. These are perfect for any areas of your home which may suffer from lack of signal (due to heavy concrete use or metal roofing, etc.).

Obviously, these aren´t such a good solution when you´re out and about!


Check out this short YouTube clip for a quick review of a signal boosting phone case –

Do phone cases block Wi-Fi / Bluetooth signal?

Well, according to Scientific American, ´Wi-Fi works off of the same principal as other wireless devices – it uses radio frequencies to send signals between devices´.

Bluetooth works in a similar manner, just at a different ´frequency´.

This means that the same types of phone cases that are likely to block phone signal (i.e. metal) will also block both Bluetooth and Wi-Fi! This is why we tend to lose Wi-Fi connection when in an elevator (elevators are obviously enclosed spaces and they´re normally built from metal)!


So, there you have it! In all honesty, any decent phone case (even if it has some metal components) is very unlikely to block your signal. Unfortunately, not all phone cases are ´decent´, so it´s always advisable to read product reviews before making a purchase (especially when buying a metal case).

If you want to know if a phone case is affecting the strength of your signal, run a test via the hidden Field Test app.