Getting a new phone on a contract is the easy option, but paying for that phone upfront and getting a SIM-only contract makes much better financial sense. Our round-up of the best SIM-only deals and best Data SIM deals in the UK could save you a fortune.

(Also, changing your SIM deal does not need to mean losing your number.)

3 Best SIM deals

Here, we've picked out our favourite SIM-only deals for light users, moderate users and heavy users to help you discover the best deals quickly and easily.

Light data users

iD 1GB data, 500 minutes, unlimited texts, 4G - £5 per month. View deal here.

Moderate data users

LIMITED TIME DEAL: iD: 4GB data, 500 minutes, unlimited texts, 4G - £8 per month. View deal here.

Heavy data users

Three: 30GB data, unlimited minutes, unlimited texts, 4G - £20 per month. View deal here.

If you're looking for more advice on how to choose a contract, or want to see some more of the top contracts picked out by our editors for light users, moderate users, heavy users and tablet users, click here. Otherwise, use our comparison tool below for SIM deals tailored to your needs.

Compare all SIM deals

Here, you can use our SIM deals comparison tool to help you find a contract that suits you. Use the sliders and drop down menus to adjust your preferences and see which networks offer a contract that'll suit you and your budget. If you're on mobile and can't see the comparison tool below, click here to refresh for an optimised version of the page.

Which SIM-only tariff do you need?

Unlike smartphone contracts, which typically stretch to 24 months, SIM-only deals are much shorter. Most SIM-only deals come with 12-month contracts, but you can also get rolling monthly contracts – sometimes at the same price or just a few pounds more expensive – that are ideal for visitors to the UK.

The price you pay per month will largely depend on how many minutes and texts you need, and how much data you require. Plus, you'll need to decide whether you need 3G or 4G data and whether your SIM is to go in a tablet (in which case you'll only need data) or a smartphone (in which case you'll want minutes, texts and data).

It's worth noting that most operators don't allow you to simply take your SIM out of your smartphone in a tablet. They also often frown upon tethering.

While 4G is much faster than 3G connectivity, 4G data is sometimes more expensive than 3G data. However, just because your phone or tablet might support 4G, it doesn't mean you have to take advantage of that connectivity if it can save you money not to. Some carriers charge the same amount for 3G and 4G data, though.

Pinning down what is the best SIM-only smartphone deal is tricky due to the huge number of combinations of minutes, texts and data available.

However, most people will fall into one of three camps that we'll focus on here: those who simply want to make the odd call or text, and use their PC to go online; those who make calls and texts, go online, check emails, use apps and perhaps watch the odd video; and those who are permanently glued to their smartphone.

Or, to put that more simply, light-, moderate- and heavy users.

SIM deals for light use

There are plans available for just £5 per month if you plan on using your SIM for light use.

We'd recommend considering iD, which is Carphone Warehouse's mobile network. All of iD's contracts offer bill capping, data rollover and Roam like at Home making it an even more appealing option with no nasty surprises.

A good option for light users is its 1 GB option, which is just £5 per month:

  • iD: 1GB data, 500 minutes, unlimited texts, 4G - £5 per month. View deal here.

SIM deals for moderate use

For moderate users, the best deals tend to be around the £10 mark for SIM-only plans.

Three offers a really good moderate SIM-only deal. For £10 per month you can get 4GB data, unlimited minutes and unlimited texts on a 4G for 12 months.

However, this is an Essential plan so you won't get personal hotspot allowance, the ability to use your data across the globe, or the Go Binge feature that lets you use TV and music streaming services without eating into your data allowance.

  • Three: 4GB data, unlimited minutes, unlimited texts, 4G - £10 per month. View deal here.
  • LIMITED TIME DEAL: iD: 4GB data, 500 minutes, unlimited texts, 4G - £8 per month. View deal here.

SIM deals for heavy use

For anyone who wants the freedom to text and use the internet as much as they like, our favourite deal is Three's 30GB data, unlimited texts and unlimited minutes contract, which is a very reasonable £20 per month.

  • 30GB data, unlimited minutes, unlimited texts, 4G - £20 per month. View deal here.

Three also offers a 12GB option for £15. View deal here.

Tablet plans (Data SIMs)

You can't simply take the SIM out of your phone and stick it in your tablet. You need to get a SIM that uses a data-only plan (and don't forget that not all tablets offer SIM-card slots, in which case you'll only be able to connect to WiFi).

How much data you need will very much depend on the activities you intend to enjoy on your tablet, plus whether you spend any of your time within range of a Wi-Fi hotspot. If you want a SIM just to cover you on the odd occasion that you use your tablet away from home and need to continue to access your email, you certainly don't need to pay out extra for a 4G plan.

Some of the best SIM-only deals for tablets come from Three, which offers 1GB for £7.50 per month, 2GB for £8 per month, 20GB for £15 per month. You can view those deals here.