By Three’s £18 unlimited data SIM is the cheapest way to get unlimited data from a major UK network. Compare Three’s unlimited data plans.
In the UK, Three is currently offering unlimited data for just £18 per month (reduced from their normal price of £24 per month).
This is currently the cheapest way of getting unlimited data from a major UK network and it’s an exclusive deal that’s only available when you order through this link. That’s because it’s a ‘hidden’ deal that won’t find when you go directly to Three’s website.
Alongside the £18 unlimited data SIM, Three also offers a range of other unlimited data deals. This includes unlimited data SIMs with inclusive European roaming (from £27 per month), and with worldwide roaming in 160 destinations (from £32 per month). There are also some Pay As You Go deals.
In this article, we’ll review Three’s unlimited data plans, including their £18 unlimited data deal. We’ll also look at their fair use policy, the coverage that’s available, and how you can keep your phone number on Three.
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Three’s £18 Unlimited Data Plan
If you’re looking for unlimited data on a major UK network, the cheapest plan currently available is Three's £18 deal. For comparison, you’ll pay at least £24 per month for unlimited data on EE, £30 per month for unlimited data on O2, and £27 per month for unlimited data on Vodafone.
Three’s £18 per month unlimited data SIM is available on a 12-month contract when you order through the link below:
| Plan | Data | Monthly Cost | |
|---|---|---|---|
Lite
| Unlimited data | £18.00 per month 12 month contract Monthly cost rising to £19.50 on 1 Apr 2026 | See deal |
With this £18 per month unlimited data deal, you’ll get all of the following included:
Unlimited data with no hidden limits. According to Three, you’ll get truly unlimited data with no hidden fair usage limits or caps in the UK. That means you can use as much data as you like, without the need to worry.- Share your data via tethering & personal hotspot. You’ll be able to tether and use personal hotspot on Three’s unlimited data plan, meaning it’s possible to share your unlimited data with other people or other devices (e.g. with your friends and family, or with a laptop or tablet).
- Access to Three’s fastest available speeds on 5G. You’ll get access to Three’s 5G network (if you have a 5G-ready phone), and access to their fastest available speeds. Recent speed tests have measured the average download speed on Three’s 5G network to be 228Mbps (H1 2025). This makes them the UK’s fastest network for 5G.
- Three+ rewards. You’ll get access to the Three+ rewards app for exclusive offers and discounts. For instance, you’ll be able to get a £1 coffee every week, along with discounted cinema tickets and meals outside.
The main limitation with this deal is that you won’t get any inclusive roaming. Instead, you’ll need to pay an extra £2 per day to use your phone in Europe, and between £5 per day and £7 per day in most other countries. If you’re looking for a deal with inclusive roaming, you could consider Three’s Unlimited Value or Unlimited Complete plans (listed below).
It’s worth mentioning that the £18 per month offer is a ‘hidden’ deal that you won’t find directly on Three’s website. The same plan will cost you £24 per month if you follow the listing on Three’s website.
Other Unlimited Data Plans
One disadvantage of Three’s Unlimited Lite plan is that you won’t get international roaming included on it.
On the Lite plan, you’ll need to pay an extra £2 per day to use your phone in most European countries. Outside Europe, the daily fee will typically be either £5 or £7 per day, depending on the destination.
Unlimited Data with European Roaming
For inclusive roaming in 49 European destinations, you can upgrade to the Unlimited Value plan. This will allow you to use your UK minutes, texts, and data in Europe (up to 12GB per month).
You’ll also get Paramount+ included for half of your plan (e.g. you’ll get 6 months of inclusive Paramount+ on a 12-month plan, and 12 months of inclusive Paramount+ on a 24-month plan).
| Plan | Data | Monthly Cost | |
|---|---|---|---|
Value
| Unlimited data  
| £27.00 per month 24 month contract Monthly cost rising to £28.50 on 1 Apr 2026 £30.00 on 1 Apr 2027 | See deal |
Value
| Unlimited data
| £28.00 per month 12 month contract Monthly cost rising to £29.50 on 1 Apr 2026 | See deal |
In general, we think it’s worth weighing up how much you’ll save with the inclusive European roaming, versus getting the cheaper ‘Unlimited Lite’ plan and just paying the £2 daily fee when you travel to Europe. For most people, we think the ‘Unlimited Lite’ plan will still work out to be cheaper overall, unless you regularly spend a lot of your time abroad in Europe.
When you buy a new mobile phone on an Unlimited Value plan, you’ll also get an extended handset warranty (up to 36 months). For more information, see our guide to Three’s Value plans.
Unlimited Data with Worldwide Roaming
For inclusive roaming in a massive 160 destinations around the world, you can upgrade to Three’s Unlimited Complete plan. It’s a great option if you regularly travel abroad, as you can use it pretty much everywhere you go. You can save up to £7 per day when you travel abroad with this plan.
On this plan, you’ll also get Paramount+ included at no extra cost (worth £4.99 per month).
| Plan | Data | Monthly Cost | |
|---|---|---|---|
Complete
| Unlimited data 
| £32.00 per month 24 month contract Monthly cost rising to £33.50 on 1 Apr 2026 £35.00 on 1 Apr 2027 | See deal |
Complete
| Unlimited data
| £33.00 per month 12 month contract Monthly cost rising to £34.50 on 1 Apr 2026 | See deal |
When you buy a new mobile phone on the Unlimited Complete plan, you’ll get an extended warranty (up to 36 months), and an inclusive screen repair if needed. For more information, see our guide to Three’s Complete plans.
Unlimited Data with No Contract
It’s also possible to get unlimited data on Three’s Pay As You Go service. You’ll pay £31.50 per month for this, with the benefit of there being no contract and no credit check needed to sign up. You’ll also get inclusive roaming in 71 destinations (up to 30GB per month).
| Plan | Data | Monthly Cost | |
|---|---|---|---|
Pay As You Go
| Unlimited data
| £31.50 per month No contract | See deal |
A small discount is available on this price, when you pay upfront for 3 months. With this discount, you’ll pay £90 for 3 months of unlimited data. This works out as £30 per month.
Fair Use Policy
On Three, there’s no fair usage limit for unlimited data when you’re inside the UK. Instead, the main restriction is that you can’t use the service for “commercial, resale or fraudulent purposes”.
Is there any limit on Unlimited data?
There’s no hidden caps or limits when you use Unlimited in the UK. You’ll get all the access to the internet you’d normally need, without hefty bills. So you can binge to your heart’s content. But use of our services for commercial, resale or fraudulent purposes isn’t allowed. You can read more about this in our Terms for Three Services.
Three has been offering unlimited data plans in the UK since 2010. Previously, these plans were referred to as having all-you-can-eat data to emphasise the fact there were no hidden fair usage limits.
Prior to September 2019, Three had a 1,000GB per month threshold that was used to identify non-permitted commercial usage of their service. Three has confirmed to us in writing that this 1,000GB per month threshold is no longer in place, with all of their unlimited data customers now having no data caps on their plan.
Network & Coverage
On Three’s unlimited data plans, you’ll get access to their 4G & 5G network across the UK. This consists of 99.8% population coverage on 4G, as well as 5G coverage to more than 60% of the UK’s population. To see the coverage that’s available in your area, enter your postcode on Three’s website.
Check Three Coverage (three.co.uk) →
In general, Three tends to receive positive feedback for the download speeds on their 5G network, with recent studies putting their average download speed at 228Mbps (H1 2025).
On the flip side, they’ve historically had more ‘notspots’, or locations where you’re unable to get a signal from them (especially in more rural areas). This is because they’re the smallest of the UK’s four main networks.
As of 2025, Three has merged with Vodafone and the two networks have gradually started to combine their coverage. As such, customers on Three’s unlimited data plan should see coverage improvements as a result, with Three’s mobile signal gradually becoming available in all areas that have a Vodafone signal. In our opinion, this negates one of the biggest disadvantages of Three.
Keeping Your Phone Number
If you’re joining one of Three’s unlimited data plans, it’s a straightforward process keeping your current phone number.
Start by asking your current mobile network to give you a PAC Code. You can get one by texting PAC to 65075, or by requesting it online through your mobile network’s website or app. You can then order your new phone or SIM card from Three’s website.
When your new phone or SIM card arrives from Three, fill out this form on their website. After submitting your PAC Code through the form, Three will schedule the transfer of your phone number (normally for the next working day). In the meantime, you’ll continue to receive a service from your old provider.
For step-by-step instructions on transferring your phone number to Three, please select your current mobile network from the drop-down menu below:
For more information, see our full guide to transferring your phone number between networks.
More Information
For more information about unlimited data on Three, please see Three’s official website.
You may also find it useful to see our in-depth guide on Three’s hidden SIM-only plans, and our full comparison of unlimited data plans in the UK.
Dave Johnson said:
I tether my smart tv to my phone as broadband is not in our area. I have absolutely no problem doing this.
3s supply is perfect, so much so I bought a sim only for my wife and she to has no problem.
3 are the best supplier I’ve ever used.
graham dale said:
i just have the 3 router/dongle but keep running out of data is there a unlimited data deal for me to upgrade to?
Ken replied:
Hi Graham,
Thanks for your comment. If you like, you can order an unlimited data SIM card from Three for £16 per month, which you can use inside your router or dongle.
Hope this helps,
Ken
Melany said:
After being with Tesco for 6 years, I thought long and decided to go with three. This was January this year.
In the beginning first 4-5 weeks everything seemed fine with my all you can eat data, but now I am certain it is throttled. I’m using my phone as hotspot, and right now, as I type, I’m struggling to download the three app.
The speed is reading 0.53mbps with a ping of 480ms..shambles.
I’ve been trying to download the three app for the past hour, as stupidly, it’s the only way you can contact three…due to coronavirus they say.
But they haven’t stopped or reduced the monthly charge they take out of my account.
Terrible absolutely terrible