Are you in a possession of a 4G SIM card, but you now have a 5G phone?

You may be wondering if you can simply pop up your old SIM card, and put it into your new phone. But will this cause any issues? What is the best way to go about it?

In this article, I’ll cover everything you need to know – along with how you can achieve 5G speeds, without having to get a new phone number.

Will A 4G SIM Card Work Inside Of A 5G Phone?

SIM Card

Yes – a 4G SIM card will work perfectly fine inside of a 5G phone, as long as both phones use the same size SIM.

Currently, SIM cards come in three different sizes – standard, micro, and nano. While you may be able to buy an adapter if your card is too small, the SIM should work fine as long as it fits in the phone.

There is one other downside, however.

4G SIM cards are only capable of running on up to the 4G network.

This means that even though your phone is technically capable of running 5G, it won’t be able to connect to 5G while it’s using a 4G SIM.

If you live in an area with 5G coverage, this means you’ll receive lower potential speeds than what your phone is actually capable of. Of course, this may not be a problem – 4G is still very fast!

More on the differences between the two networks later.

Your Phone Isn’t Always Connected To 5G, After All

If you think about it, it actually makes a lot of sense that the 4G SIM would still work.

After all, 5G coverage is still rolling out across the United States, and many areas of the world don’t have it at all.

When the 5G network isn’t available, 5G phones will automatically connect to the best network available – usually 4G.

So, even if you had a 5G SIM, you’d still be running on the 4G network a lot of the time anyway.

If you owned a 4G phone before upgrading to a new one, you should expect roughly the same coverage and speeds as you had previously – as long as you didn’t also change cellular providers, of course.

Therefore, if your older speeds were acceptable, you really have nothing to worry about.

Of course, getting onto the 5G network isn’t actually that hard, and doesn’t require you to change your phone number!

Have A 5G Phone? Get A New SIM!

If you’re upgrading to a 5G phone, the solution to all of this is simple – get a new SIM card!

Contrary to popular belief, a new SIM card does not mean a new phone number. You can request a new or replacement SIM from your carrier, and still keep the exact same phone number that you had previously.

This is completely normal, and happens with phone upgrades all the time. Carriers know exactly how to handle the situation, and even if you have to pay for it, SIM cards are only a few dollars.

Certainly a small price to pay to get onto the 5G network!

Keep in mind however that you can only have one active SIM at a time.

Therefore, once you receive a replacement SIM card and it’s active, your old SIM card will no longer work.

A standard phone call can only go to one phone at a time, after all!

4G Vs 5G Speeds

So, how drastic are the differences between 4G and 5G speeds? Is it really worth taking the time to upgrade, even if it means waiting for a replacement SIM to arrive in the mail?

Personally, I think so – especially when you consider the fact that the 5G network is still rolling out!

As far as speeds go, the differences are quite significant.

In perfect conditions, 5G speeds can reach download speeds of over 1 gigabyte per second, and can theoretically end up being 10 to 20 times faster than peak 4G speeds, according to analysts.

Currently however, the difference is still significant, but not quite as drastic.

On AT&T for example, average real-world test results for 4G clocked in at 75.6 megabytes per second for 5G, and 37.1 megabytes per second for 4G. Other carriers like Sprint, T-Mobile, and Verizon had similar results, as of 2020.

In the 1st quarter of 2023, T-Mobile achieved median 5G download speeds of a whopping 220.7 Mbps, showing that 5G speeds have improved a lot over the past few years!

This already is 6x faster than average 4G speeds, making the difference quite enormous!

Of course, your results may vary depending on your network and coverage.


Thankfully, 4G SIM cards will work perfectly fine inside of a 5G phone – as long as they are the right size.

However, you will not be able to connect to the 5G network until you upgrade to a 5G-capable SIM card. The difference in speeds are quite dramatic, so I highly recommend doing so!

I hope that you’ve found this article helpful, and that it’s answered all of your questions.

If you have any other questions about SIM cards, ask them below and I’ll be happy to help.

Wishing you the best,

– James McAllister

About the author 

James McAllister

James is the owner of He started his first blog at the age of 11, and has since gone on to start several successful businesses. In total, these businesses have sold hundreds of thousands of units and have touched millions of lives. Here on, he shares his knowledge that brought him to where he is today. If you want to connect with James, follow him on your favorite social networks!

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