BT Mobile vs O2: 5G/4G coverage, speed and perks compared

✔ O2 have the advantage for calls

O2 own and operate on their own network, where BT own EE and so use their network for signal. Both these networks have pros and cons for signal coverage of the UK.

In terms of call signal (2G/3G) O2 hold a clear advantage, especially indoors as they broadcast on frequencies that are better for getting through building materials. You generally get better call signal in rural areas too.

However, BT have more of the country's physical landmass covered than O2 for 4G signal. This shouldn’t make much of a difference in urban areas, but as you travel around you’ll get stronger 4G on BT than on O2.

Signal varies on every network in different locations so we recommend checking both their network maps here. Check everywhere you’ll expect to use your phone, not just at home.

Useful link: Use O2’s coverage checker

✔ BT benefit from EE’s excellent 5G coverage

BT have access to EE’s growing 5G network, while O2 have been rapidly expanding their own. EE have declared 160+ locations covered with 5G while O2 have the second highest number of covered locations with 190+.

This doesn’t tell the whole story, however. EE only declare a location covered when 5G is available in 50% of that location’s area, where O2 will declare it covered much earlier.

The effect is BT tend to have better coverage in their declared locations than O2. And with BT, you might even get 5G in some locations that aren’t on the declared list, so O2’s higher number isn’t all that meaningful.

It’s always worth giving their coverage checkers a go to see which network best covers your area.

Useful link: Check BT’s coverage in your area

✔ BT Mobile should have faster speeds overall

Since you’ll be on 4G more often than 5G, it’s important to look at a network’s average 4G speeds. Opensignal say BT have average speeds of 44.0 Mbps, while on O2 you can expect speeds of 17.1 Mbps on average.

That’s a massive difference. O2’s speeds are still typically good enough for your regular browsing needs, but downloading big files and streaming HD video will be a lot easier on BT.

In terms of 5G it’s a little closer. Opensignal and Speedtest by Ookla put BT’s 5G speeds between 131.9 Mbps and 144.5 Mbps. O2’s were a bit lower at 110.9 Mbps to 141.3 Mbps.

Their 5G speeds aren’t massively different, but you can expect faster speeds on BT in general. Remember, these are average speeds and your actual speeds may be much higher or much lower than these.

Useful link: BT’s guide to their 5G

✔ BT Mobile's WiFi calling is one of the best

As we stated, BT don’t broadcast their 2G/3G signal on ideal frequencies for getting into buildings. Thankfully, they have a great WiFi calling and 4G calling provision to help out with this.

The feature will work as soon as you put your SIM into a supported device (see list here). It comes on every plan at no extra cost as well. But how does it compare to other networks?

Well, you can move from WiFi signal to 4G signal without dropping your call, you can send/receive SMS messages and it pairs incredibly well with their brilliant 4G coverage and WiFi hotspot provision.

The only potentially bad thing is that we can’t say for sure which Android models will work. If a model is listed it will work. We tried models that weren’t listed and they worked just fine, but this won’t always be the case.

Useful link: Our list of the best WiFi calling networks

✔ O2’s WiFi calling is a bit limited

If you really want to be able to send/receive SMS messages over WiFi then O2 won’t be for you, they don’t allow it. If you don’t mind missing out on this, their WiFi calling is still worth looking at.

You can move from WiFi signal to 4G signal without dropping your call, which is always great. Their WiFi calling also pairs well with their decent free WiFi hotspot access.

There’s a few cracks that limit this feature. As we said, there’s no SMS messaging over WiFi and you’ll only get it on their pay monthly phone and SIM only deals, not on their pay as you go plans.

O2’s list of supported devices is also quite limited still, especially for older Android models. We did find that some test models worked despite not being listed, so we can’t really say if they support more or fewer models than BT.

Useful link: Read O2's full guide to WiFi calling

✔ BT have the UK’s largest WiFi hotspot network

We really appreciate when a network offers free WiFi as a way of staying connected on the go. It’s a great way to hold onto your data while still being able to browse to your heart’s content.

BT offer by far the best WiFi hotspot provision in the UK. Being on any of their pay monthly phone or SIM only deals gets you access to a network of 5 million hotspots around the UK.

These hotspots usually cover popular areas such as restaurants, airports, high streets and so on. Using their BT WiFi app will get you connected automatically to your nearest hotspot.

This automatic log-in feature can leave you on a weaker signal than just staying on mobile data. But, you’ll generally find their WiFi to be a slick way of keeping connected without eating into your data.

Useful link: More about free WiFi on BT Mobile

✔ O2 also have a decent WiFi hotspot network

O2 are another network to offer free WiFi hotspots. On all pay monthly and pay as you go plans you’ll get free access to a network of about 15,000+ hotspots across the UK.

You can actually connect to these without being an O2 customer, but if you are an O2 customer your SIM will be automatically detected and will connect to the nearest hotspot. You don’t have to do anything manually.

Unfortunately this automatic connection only works on about 7000+ of these hotspots, not all of them. Also the same issue applies that you may connect to a hotspot that has far worse connection than being on data.

Still, it’s a decent enough provision for saving a bit of data where you can. We really like that there are hotspots on the Underground, as BT don’t provide them there.

Useful link: O2’s full guide to their WiFi hotspots

✔ O2 offer worldwide roaming on some plans

O2 have kept their EU roaming in place. You can use your regular UK allowance of minutes, texts and data in these EU destinations. However, you will be limited to 25GB while you’re there if your plan is over that amount.

But not only do you get roaming in the EU, but you can also roam in 27 worldwide destinations if you take select SIM only or phone plans. These tend to be pricier plans and the benefit is added as an extra.

O2 SIMs with extra roaming

All these plans get you access to O2’s Travel Inclusive Zone

You won’t get access to your regular UK allowance in their Travel Inclusive Zone. Instead you’ll be limited to 120 minutes, 120 texts and a small amount of full speed data (we think it’s 150MB).

Once you run out of data in their inclusive zone you’ll get unlimited data, though it will be severely speed capped. O2 offer both a good EU roaming scheme and a decent worldwide roaming scheme for short stays.

Useful link: O2's full guide to roaming and costs

✔ BT Mobile get you EU roaming on all plans

BT have also kept their EU roaming scheme in place. On all of their plans you’ll be able to access your regular UK allowance in these 46 EU destinations.

They do impose a fair use policy of 50GB on plans over that amount, with smaller data plans you can use your whole allowance abroad. That’s still a lot of data and should be more than enough for a short trip.

BT also offer some daily data add-ons for worldwide travel. This gives you 500MB of data for £6 a day in 12 worldwide destinations. That’s not incredible value, but it’s much better than paying their international rates.

For our real-life BT review, we find roaming on BT in the EU really good. It all works fine automatically. You get 4G wherever it’s available.

Useful link: Learn more about Roam Like Home

✔ BT's Family SIMs give discounts the more deals you add

If you want to put your kids on a mobile plan, it’s good to think about which networks offer the best family mobile plans. These can get you discounts on extra plans added onto one main account.

BT offer a really good family plan. It lets you add up to 4x select SIM only plans on your account with each extra SIM getting you an even bigger discount (calculate savings here).

What makes this even better is that these extra SIMs are all on 30-day contracts. This means you can add and drop them with almost no notice. You get great flexibility in managing your account, which is what family plans are all about.

The big drawback is that all extra SIMs need to have the same data amount as each other. We don’t think this is realistic for most families, as some users will need more data than others. But overall, it’s a good scheme.

Useful link: Read our full review of BT's Family SIMs

✔ O2 offer discounts on up to 20 plans!

O2’s multisave is a pretty simple scheme to understand. You get a flat 20% off the cost of any extra SIM only plans or off the usage (minutes, texts, data) of any phone plan added to your account.

It’s a little fiddly to set up, but once you’ve added the extra plan to your account you’ll get 20% off that plan when your monthly bill comes. Bear in mind the discount won’t be applied to the account holder’s plan, only extra plans.

What’s amazing is that you can potentially add up to 20 extra plans. We say “potentially” because you will have to pass a credit check. You’d have to have basically spotless credit history to add that many plans to your account.

O2 also used to let you share data, but they’ve said they’re going to halt this as a feature. If you already have a plan that lets you share then you can keep doing it. But now they’ve made it harder to get sharer plans.

Useful link: Read O2’s full guide to their multisave scheme

✔ O2's phone contracts are more flexible

O2 offer some of the best flexibility of all networks when it comes to phone contracts. You can tweak your contract with them to change your contract length (anywhere between 3 and 36 months) and upfront costs.

Their contracts are based on finance agreements where you have one payment for the cost of your phone and another for your usage. This means you can upgrade by paying off your phone’s cost before your contract is up.

BT’s phone contracts are only offered on 24-month contracts. Because they’re not based on finance you can’t upgrade early and the cost of your usage and phone are bundled into one.

O2 may offer greater flexibility, but you’ll also have to pass a credit check. This can be difficult if you have any missed payments on your credit history. You can use our comparison tool below to see which network is best for price.

Useful link: Full details on O2's custom plans from their own guide