The Best Three SIM Only Plans in October 2021

Three has a great range of competitively priced plans for all types of mobile customers. Read on to find the right plan for you.

three best sim only plans 2021

Three offers market-leading pricing for SIM only plans, big data plans and unlimited data plans. Objectively speaking here, Three SIM only deals are generally priced below the other UK Mobile Operators.

Three September 2021 OfferLatest  Offer: 12GB Data for just £8/Month SIM Only

Three is offering customers 12GB data with unlimited UK minutes and texts for just £8 a month! The deal is a 12-month contract. There are no data or speed caps.

With this Half Cooked Exclusive Deal you also get 5G at no extra cost as well as access to Go Roam. Click through to ensure you don’t miss out!

In this article, we will help you establish what type of mobile user you are and help direct you towards the best SIM only plans available on Three. For this article, we’re assuming you’re already happy with the basics of the network including coverage and speeds in your area, but in case you haven’t you can always read our extensive Three Review to learn everything you need to know.

Be it unlimited data SIM only deals, large data plans or smaller data plans Three’s got you covered. Plus, all of Three’s SIM only deals come with 5G at no extra cost, Three Go Roam (free roaming in 71 countries), 4G Calling, Wi-Fi Calling, unlimited UK calls & texts.

Having said all that, you should know that there are no reward programmes on Three, and the carrier doesn’t offer any 2G coverage. Their 3G and 4G coverage is also behind the other major operators.

Keep reading to pick out the most suitable Three SIM only deal for you.

Table of Contents

1. Plans and Pricing

– Best Three SIM Only Plan For Light Data Users

– Best Three SIM Only Plan For Moderate Data Users

– Best Three SIM Only Plan For Heavy Data Users

– Best Three Unlimited Data Plan

– Cheapest Three SIM Only Plan

-Best Three SIM Only Plan For International Roaming

– Best Three SIM Only Plan For Tethering

– Best Three SIM Only Plan For Students

2. Network Coverage & Data Speeds

– 4G &3G Coverage

– 5G Coverage

3. How Much Mobile Data Do I Need?

4. Can I Keep My Phone Number?

5. Frequently Asked Questions

Plans and Pricing

Three covers all contract terms, offering 1-month, 12-month and 24-month contracts, a traditional pay as you go service that requires no credit checks as well as pay as you go bundles. All of their services come with the same perks listed earlier, there are no exceptions.

Best Three SIM Only Plan For Light Data Users

If you don’t really use your phone regularly and your usage consists of checking emails, occasionally surfing the web or you’re regularly connected to Wi-Fi – you’re a light mobile data user. If that’s the case, even 1GB of data per month may be enough for you and Three’s 24-month contract would have you covered, priced at £6/month. However, you can pick up Three’s 12GB tariff for just £8 a month via Half Cooked, plus it’s only a 12-month commitment. The 12GB data plan is priced at £13 a month on Three’s official website, so you’ll be saving £5/month with us.

Keep in mind that 1GB of data can be burnt through quickly, even if you’re only an occasional user. The next biggest data plan is 4GB for £10/month, which is more expensive than our special offer above and it offers you significantly less data.Three 12GB 2021 Discount

Best Three SIM Only Plan For Moderate Data Users

Once again, our special 12GB for just £8 a month is the best choice, if you’re looking to join Three.

According to Three, their customers use about 15GB of data on average per month. We believe this is the best plan for a moderate mobile data user, but if you think you need more Three also offers a 30GB data plan. You’ll have to pay a bit more to get your hands on this deal. It’s £14/ month if you sign up for a 24-month contract, and £15 if your contract length is 12 months. Three’s 30-day contract with 30GB of data is £24/month.


Best Three SIM Only Plan For Heavy Data Users

At the time of writing, Three’s range of heavy data plans is very limited. If you’re not interested in unlimited mobile data, the best you can get is a 30GB data plan. As stated above, the 24-month option is priced at £14/month and 12-month contract is £15/month.

Three’s cheapest unlimited data plan is priced at £20 a month and it’s a 24-month contract, but since they slash their prices in half for the first six months, you’ll be paying £17.50/month on average. Alternatively, there is a 12-month unlimited data contract that is priced at £20 a month.Three Unlimited 5G Offer

Best Three Unlimited Data Plan

There are four different options to choose from, if you want to get unlimited data from Three. The first three options are pay monthly mobile contracts and the last one is a contract-free alternative that’s on pay as you go. All four deals provide truly unlimited data, no speed restrictions and no data caps.

We strongly believe, Half Cooked’s discounted unlimited data plan is the best option, provided you’re okay with signing up for a year long contract and passing Three’s credit check. The 30-day contract is £26/month, and you’ll still have to undergo a credit check. If you pick the 24-month contract you’ll pay £17.50 per month. Three Unlimited 5G Offer

If you are looking for a commitment-free unlimited data option on Three, the network offers an Unlimited Data Pack, priced at £35/month. If you’re after a contract free option, we’d recommend checking out SMARTY’s unlimited data plan. The MVNO is powered by Three, and their unlimited plan is significantly cheaper. However, SMARTY doesn’t have 5G yet and there’s a fair usage limit of 1000GB on their unlimited plans. You still get Wi-Fi Calling with SMARTY, but there’s no 4G Calling either. Still, we think getting unlimited data for just £20 a month with no credit checks is a great deal.


Cheapest Three SIM Only Plan

If you’re a light mobile data user, and you just need a SIM to keep your phone active we’d recommend checking out Three’s old school pay as you go service. Having said that, there are much cheaper traditional pay as you go offers on the market from carriers such as 1p Mobile and ASDA Mobile and they both offer better network coverage and higher voice call quality.

Alternatively, you may want to sign up for a 24-month contract and get Three’s 1GB data plan. That’s the cheapest pay monthly option on Three, but we think it’s a bad investment. 5G will increasingly be available across the UK leading to more usage of data, and even now 1GB is barely enough for the lightest activities on the web. Thankfully, you can upgrade to a larger data plan without having to cancel your mobile contract with Three.

Best Three SIM Only Plan For International Roaming

Well, since all Three plans (including PAYG deals) come with free roaming in 71 destinations across the world -thanks to Three Go Roam– we believe all their offers are great for international roaming.

The mobile network’s free roaming scheme is identical on all their deals, unlike EE, O2 and Vodafone, where you can get premium deals that include more roaming destinations.

In Three’s Go Roam in Europe destinations, you can use up to 20GB of your mobile data allowance at no extra cost, but beyond this point, you’ll be subject to a surcharge. In Go Roam around the World destinations the fair usage limit is down to 12GB. In these destinations you can send 5000 texts back to the UK. You can also use up to 3000 minutes on calls back to the UK.

Three PAYG customers with data packs are subject to identical fair usage limits.


Best Three SIM Only Plan For Tethering

Tethering refers to turning your mobile phone into a personal hotspot or a router, allowing other compatible devices to use your mobile data. It’s a great feature, but this also means your data gets used at a significantly faster rate.

Tethering refers to turning your mobile phone into a personal hotspot or a router, allowing other compatible devices to use your mobile data. It’s a great feature, but this also means your data gets used at a significantly faster rate.

If you’re planning to tether on a regular basis and to multiple devices, we strongly recommend an unlimited data plan. Big data plans work too, but unfortunately, Three doesn’t offer any price plans that provide about 100 to 200GB of data at the moment.

Three Unlimited 5G Offer

Best Three SIM Only Plan For Students

At the time of writing, the only Three SIM only offer tailored specifically for students is their 100GB data plan, which is a 24-month contract and priced at £16 a month. If your area has Three 5G, we’d rather recommend opting for an unlimited data deal though. At 5G data speeds, you’ll be burn through your allowance rather quickly.

Three Unlimited 5G Offer

If you’re on a tighter budget, you can read our detailed UK student mobile plans guide and pick out the best deal for you. If you want a commitment-free, cheap SIM only plan with high value, check out SMARTY’s 10GB of data for £8 offer too. On top of that, you can start a family/group mobile plan with your loved ones and get a 10% discount on each additional deal.

Network Coverage & Data Speeds

4G & 3G Coverage

Three is one of the four main mobile networks in the UK, it means they have their own underlying infrastructure. They’re also powering other mobile networks such as SMARTY, iD Mobile and Superdrug Mobile. Sadly, Three and their MVNOs don’t offer 2G coverage, which is still a fallback option for voice calls on other operators. This also means if your device only supports 2G, it won’t work with a Three SIM.

The network provides over 99% population coverage for 4G & 3G, but so do all the other UK mobile networks. What really matters is a network’s geographical coverage and Three ranks last among the four major carriers operating in the UK. Their indoor coverage is also weaker compared to O2 and Vodafone. However, if you’re close to a mast you’ll get very good coverage regardless of where you are in your home.

On the other hand, Three’s 4G download and upload speeds are quite good, pretty much on par with Vodafone. However, there’s a huge gap between Three and EE, who have the most 4G coverage and fastest 4G data speeds in the UK. Three’s average 4G download speeds are around 22Mbps and their upload speeds are around 8Mbps, per Open Signal’s October 2020 test results.

For comparison; EE’s average 4G download speeds are around 36Mbps and their upload speeds average around 10 to 11Mbps. You can read our detailed Three vs EE article to see how these two networks compare.

three coverage map

5G Coverage

5G is becoming more prominent every day and mobile network providers are constantly increasing their 5G coverage and services. Even most MVNOs are now offering 5G plans. All of Three’s SIM only tariffs come with 5G at no extra cost, but you’ll need a 5G ready handset to benefit from the network’s superfast data speeds.

Three offers 5G in 194 UK cities and towns. This means they provide 5G in more locations than any other UK network, but their 5G coverage per location is not as wide as EE or O2.

In terms of 5G download speeds, they are one of the fastest mobile networks in the UK. Three’s average 5G download speeds are around 201Mbps, plus they have the most 5G spectrum available.

How Much Mobile Data Do I Need?

We already have an extensive guide specifically addressing this question. You can read our ‘How much mobile data do I need?’ article for a more detailed approach. In this section, we’ll be a bit more specific and just focus on Three’s SIM only offers.


These SIM only deals are good for customers who are looking to get their hands on a very cheap deal. If you mainly use your Wi-Fi, this much data can be enough. Even light data activities such as going through your emails and checking only a few web pages a day can burn through 50 to 100MB a day.


Under normal circumstances, for a moderate mobile data user 8 to 10GB should be more than enough. However, Three doesn’t have a 10GB data offer, but there’s a 12GB option. You can freely watch videos on 360p and stream music for a few hours every day on an 8GB data plan. But, why would you get 8GB for £11, when you can get 12GB for £8/month with our exclusive Three SIM Only offer. Both deals are 12-month contracts, and besides the price and data allowance, everything else is identical.


Mobile customers tend to burn through a lot more data as their download and upload speeds get faster. 30GB of data per month is the sweet spot for most users. If you’re willing to sign up for a 24-month deal, you can get it for £14 a month. Just keep in mind that for just £2 more, you can grab an unlimited data plan from Three and it’s a shorter contract, meaning you have more flexibility.

Unlimited Data

Three are known for their unlimited data plans. The network provides the best unlimited data plans in the UK. They are truly unlimited, unlike what most other providers offer and yet competitively priced. In fact Three offers the cheapest unlimited data plan in the UK for just £16 a month. On top of that, this deal comes with 4G Calling, Wi-Fi Calling, Three Go Roam and it’s 5G ready.

Neither the 30-day unlimited data contract nor the unlimited PAYG Pack are worth it though, at least in our opinion.

Can I Keep My Phone Number?

Yes you can. In the UK, you can keep your old phone number when switching to a new mobile network. There are no exceptions. All you have to do is get in contact with your current network and ask for your PAC code. Once you receive it, give it to Three and they’ll do the rest. It’s a short process, but it may take a day or two sometimes.


Three Best SIM Only Plans Frequently Asked Questions

Does Three have 2G?

No, Three doesn’t offer a 2G service. If your handset only supports 2G, it won’t work with a Three SIM. The SIM card may fit your phone, but it just won’t work.

Is Three really the fastest 5G network?

Arguably, yes. According to OOKLA ( Three is the fastest 5G operator, but Open Signal's speed test results put Three in the third spot.

Does Three Pay As You Go have 5G?

Yes, all of Three pay monthly plans and pay as you go deals come with 5G. Even the traditional pay as you go service offers 5G coverage and data speeds.

Does Three have VoLTE or 4G Calling?

Yes, Three offers 4G Calling, which is also known as VoLTE. Having said that, Three dubs this service as “4G Super Voice”. It’s just a fancy name.

Do I have to pass a credit check to join Three?

Three’s best value SIM deals are their pay monthly contracts. This means you’re required to undergo a credit check and pass. Alternatively, you can use the network’s pay as you go service and buy a data pack when you need one.