Unlimited data SIM only deals

How do unlimited data SIM only deals work?

If you hit your data limit every month, you could consider an unlimited data SIM only plan. Unlimited plans are available on most UK networks to suit most budgets.
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How do unlimited data SIM-only deals work?

Of all the SIM only options, the unlimited data option is usually the most expensive to cover the advantage of uncapped data usage. However, this does mean you can stream, play or browse without any unexpected charges.

Handsets aren’t included. Like other SIM card-only deals, you have to provide your device. This means you could end up paying less if you’re switching to an unlimited data SIM only deal from a standard phone-and-SIM tariff.

However, before committing to a new deal, there are other costs you need to factor in:

  • The price of a new smartphone, if you don’t have one
  • Any texts and calls you make each month, if they’re not unlimited or you exceed your monthly allowance
  • Any services you use or calls you make that aren’t included in your plan, such as data roaming and premium rate numbers. Some providers offer bill capping to protect you from any nasty surprises.

Unlimited data SIM only plans in the UK include: 

  • Pay As You Go: The most flexible choice with no contract and no limits on data usage. Most plans give you unlimited texts and calls too. Available from Three, Vodafone, iD Mobile and GiffGaff, among others.
  • 30-day plans/rolling monthly contracts: Enjoy fixed monthly payments but no long-term commitment. Some even come without contracts and credit checks. Plans are available from iD Mobile, ASDA Mobile, SMARTY, Tesco Mobile, Vodafone and Three. They automatically renew if you don’t cancel.
  • 12, 18, 24 and some 36-month contracts: You pay a monthly fixed amount based on an allowance that includes unlimited data, plus texts and calls. These are usually unlimited too. You’re committed to staying with that provider for the length of the contract. For 36-month contracts, in particular, you’ll be out of the market for any new deals for a long time. Unlimited data SIM only plans on longer contracts are in plentiful supply. Compare contract mobile phone deals to find your best fit.

Do I need an unlimited data SIM deal?

Not necessarily. In 2021, the average person used 5.6GB (gigabytes) a month. This was an almost 25% increase on the previous year. With the 5G rollout and the growing demand for data-hungry apps and services, you can expect today’s figure to be even higher.

However, wi-fi is also much more readily available in most public spaces as well as at home. You don’t always need to rely on data to stay connected.

Think about the apps you’re using, too. Some are particularly data-hungry, including: 

  • Peer-to-peer (P2P) file-sharing software e.g. BitTorrent
  • P2P TV
  • Streaming video services
  • Software update services.

They’re often sending and receiving data in the background, even when you're not downloading a file.

If you’re thinking about switching to an unlimited data SIM only deal, find out how much data you use each month before you sign up. You can log into your mobile account to find out.

If you want to know more about what you can do with your data, use our mobile data calculator.

What does unlimited data mean?

In some cases, it genuinely means unlimited internet access, but fair usage policies do exist. These put a limit on the data you have access to for personal use. It’s usually a high limit, so unless you’re using vast amounts of data, you’re unlikely to be affected. But there are some exceptions.

For example, EE’s fair use policy kicks in if you use your phone abroad. Data roaming is capped at 50GB. It views data usage over 600GB a month as ‘non-personal’ –  i.e. for business. 

For O2, data roaming is capped at 25GB, and its fair usage policy will take effect if you:

  • Regularly tether to 12 or more devices
  • Use 650GB twice within six months
  • Connect to devices that need to be plugged in to work

 Meanwhile, Three has no limits on data usage at all.

Network providers may also limit the speeds available. This impacts the price of your unlimited data SIM only plan.

By ‘speed’, we mean how fast your mobile data connection is in Mbps (megabits per second). Slower speeds affect how quickly your device sends and receives information. For example, data allows you to stream high-quality videos, but slower speeds make it less likely to be a smooth, ultra-high-definition experience.

EE was recently ranked no.1 for mobile download speeds in the UK, with an average of around 48Mbps. Three came second with around 35Mbps. With 5G, you’re looking at the potential for real-world download speeds of 200Mbps.

For the best possible experience, you’d need access to a 5G network at full speed. The closer unlimited data SIM only deals come to this, the more expensive they’re likely to be.

How much does unlimited data cost?

The monthly cost of a SIM only deal with unlimited 5G data starts at £15 from iD mobile with a 30-day contract.   

Other providers, including Lyca, Lebara and Honest Mobile, go even lower, from £8.99 a month, but then shoot up to £20+ a month once you’re three months in. 

Unlimited data isn’t necessarily more expensive than capped data options. For example, the iD Mobile one-month contract is the same price as 100GB of data with O2 on a 12-month contract. Plus, you have the extra flexibility of not being tied in for a year.

How much you pay depends on what you’re looking for.

  • Do you want the freedom of PAYG or a 30-day plan? Or the predictability of a longer-term agreement contract?
  • Do you want 5G (if it’s available in your area and your phone is compatible)?
  • What kind of download speeds do you need?
  • Are you interested in special offers, discounts or freebies, like customer rewards, data roaming or access to premium TV channels?
  • Could you save money with combined TV, broadband and phone services?

Comparing unlimited SIM only deals online allows you to filter results so you can find exactly what you’re looking for.

I claim benefits: Can I get cheaper unlimited data SIM only deals?

Yes. Three’s SMARTY and Voxi both offer social tariffs of £12 and £10 a month, respectively. You could be eligible if you’re claiming:

  • Universal Credit
  • Jobseeker’s allowance
  • Employment and support allowance
  • Disability Allowance
  • Personal independence allowance

I’m on social media a lot: Is unlimited data the best option for me?

Social media apps are data-hungry. Depending on what else you use your phone for, an unlimited data deal may be the best option. If being social eats up the biggest chunk of your data, Voxi’s unlimited social plans are a cheaper alternative.

On a rolling 30-day subscription, for £10 a month, you get unlimited access to seven UK social apps, plus unlimited calls, texts and picture messages. Data is capped at 30GB but none of your posts, tweets, friending and following will come out of that allowance.

What are the best unlimited data SIM only deals?

If you’re after unlimited data, most of the major networks will oblige. And 5G usually comes as standard too, if it’s been rolled out in your area. 

Here are some examples from the biggest brands. See more by comparing some of the best unlimited data SIM only deals online.


  • £31 a month
  • 12-month contract
  • Texts and minutes: Unlimited
  • Extras: VeryMe Rewards app


  • £20 a month
  • 24-month contract
  • Texts and minutes: Unlimited
  • Extras: Three+ loyalty app


  • £35 a month
  • No contract or 18-month contract
  • Texts and minutes: Unlimited
  • Up to 5GB of free data in the EU and selected destinations

Tesco Mobile

  • £30 a month
  • 12-month contract
  • Texts and minutes: Unlimited
  • Flexible cap on spending

Honest Mobile

  • £11.25 a month, increasing to £22.50 after three months
  • 12-month contract
  • Texts and minutes unlimited
  • Extras: Carbon-negative and monthly bill reductions