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What is a SIM-only plan?
More and more mobile phone users are opting for a SIM-only plan over a longer mobile contract - particularly as smartphone technology has improved and people feel less inclined to change their handset every year.
A SIM-only plan gives you a SIM card, an allowance of call minutes, texts and data, but no phone. This means you can keep your old handset and shop around different mobile providers for a plan that suits your needs.
You can choose from a wide range of SIM-only plans - some favour call time and texts over data, while others focus on big data allowances.
Unlimited data sim contract deals explained
An unlimited data SIM-only plan means you get as much data as you can use. You can stream music, watch videos, listen to podcasts, spend all day on social media… basically do all the things on your phone that suck up data without worrying about hitting a limit or having to pay for more megabytes.
While there are only a handful of networks who offer unlimited data SIM-only plans, many networks provide good plans with high data allowances - between 20-50GB. If you know you're going to need a lot of data each month, don't get too fixated on unlimited plans. It's likely that a plan with a high data allowance will still meet your needs.
For that reason, as well as unlimited data SIM-only plans, we recommend heavy mobile data users should consider plans that include high data allowances between 20GB and 50GB.
What's good about unlimited and big data SIM-only deals?
Simply put, you can forget about how and why you use mobile data.
Serial Netflix watcher - fine; Spotify addict - no problem; facebook botherer - you're good.
If you don't have to worry about how much data you're using, then you have no concerns about going over a data limit and being penalised for it. You can download and stream without limits. But we're all different, so whether an unlimited or big data SIM-only deal is the right plan for you all depends on how you use your phone.
What's bad about unlimited and big data SIM-only deals?
The main drawback of an unlimited or big data SIM-only deal is the price - understandably networks aren't giving them away. You're getting more data and so you should expect to pay more for it. It's important you do some research and find out what your average data use is each month. If you're averaging between 2-5GB data use, there's no point paying out for 40GB. Your data use will fluctuate but you should still be able to get a rough idea of how much data you get through.
Compare unlimited data sims by network
You can use our deals table to compare unlimited or big data SIM-only plans by network.
There are currently only a handful of networks who offer unlimited data SIM-only deals - Three, Virgin Mobile and giffgaff. However, most networks offer big data SIM-only deals which could equally cater for your data needs.
Find an unlimited or big data SIM-only plan by network:
Asda Mobile SIM-only deals
All Asda Mobile's plans are pay-as-you-go and SIM-only, and since Asda uses the EE network, coverage is excellent covering 99% of the UK population. Their big data SIM-only deals are competitively priced and come with unlimited texts and calls.
EE SIM-only deals
With a good range of monthly SIM deals with varying data allowances, EE also has wider coverage than any other UK network. All of EE's SIM-only plans come with unlimited minutes and texts, and its largest data SIM-only deal comes with a massive 40GB of data.
giffgaff SIM-only deals
Keeping its deals simple, giffgaff offers probably the best value for money on SIM-only plans. With excellent medium-data use SIMs that include unlimited texts and calls, their prices are hard to beat. Be aware that although giffgaff advertises unlimited data, they will slow your connection down after you use a certain amount.
iD Mobile SIM-only deals
Offering good value for money, iD Mobile's SIM-only tariffs are all flexible 30-day rolling plans. They also include handy benefits such as data capping, data rollover and inclusive EU roaming.
O2 SIM-only deals
Monthly data allowances on O2's SIM-only deals range from 200MB to a massive 50GB. SIMs are available on either a one-month or 12-month contract, and a O2 plan also gets you exclusive offers on tickets and offers.
Tesco Mobile SIM-only deals
Catering for most data, minutes and text needs, Tesco Mobile has a decent variety of SIM-only deals - reasonably priced plans which include benefits such as contract caps, Europe roaming and Family Perks like extra data or discounts.
Three SIM-only deals
One of the few networks to offer unlimited data SIM-only deals, these plans also include unlimited texts and calls and can be taken out for 30 days or for 12 months. Depending on the plan, Three SIM-only customers also receive certain additional benefits.
Vodafone SIM-only deals
As you'd expect from one of the UK's biggest mobile providers, Vodafone offers a huge selection of SIM-only deals - particularly if you have big data needs. Choose between a one-month or 12-month contract and keep an eye out for its Vodafone Red plans, which include great extras such as subscriptions to entertainment apps such as Spotify, NOW Broadband or Sky Sports.
How much data do I need?
Mobile data use is affected by most of the activities we use our phones for - sending and receiving email, using WhatsApp, playing games online, streaming music and watching video will all ramp up your data use. So how much data do you need? There's no simple answer to this and it all depends on how you use your phone.
If you're a light user who, on a daily basis, sends some emails, browses the web and occasionally uses social media, then 1GB of data should be adequate. Medium users who use their phone to watch a few videos, use a lot of apps and regularly browse the web should consider a data plan around 3-5GB. It's only if you watch a lot of video, stream music, send documents back and forth, and listen to hours of podcasts on your phone, that you should think about unlimited or big data SIM-only plans.
How can I find out how much data I need?
Take a look in your phone's settings at your data usage stats to see your current monthly data use. Are you consistently going over your current data limit? Then it may be time to consider a SIM-only deal with a higher data limit. Or download a data usage app for a more comprehensive overview of how you use mobile data and which apps suck up the most data.
What is the network coverage like in my areas?
Before you select a SIM-only plan with a mobile network, it's important to find out who offers the best network coverage in your area and the areas you regularly visit. Mobile network coverage in the UK is improving all the time but there are still odd gaps here and there, particularly outside towns and cities. Poor network coverage can be frustrating, so it's worth checking this before you sign up to a plan.
You can find out which networks offer the best coverage in your area by using our Mobile Coverage Checker.
Find the cheapest unlimited and high data allowance SIM deals
Use our deals table to find an unlimited or big data SIM-only plan. Click on SIM-Only plans and then filter the results using allowances for minutes and texts and most importantly data allowances - from 500MB to unlimited data.
You can also search plans by network and contract length. SIM-only plans tend to be 30 days or twelve months in length.
Can I keep my old number?
Yes, it's easy to keep your number. Once you've decided on your new mobile contract, you'll need to ask your existing network for a PAC code (Porting Authorisation Code). It's usually three letters and six numbers long and won't cost you a thing. You now have 30 days to pass this code to your new network supplier, who will then port the number from your old SIM to your new SIM, which means you can keep using your existing mobile number.