New 'build your own contract' tool for mobile phones launches

The 'Build your own*' tool – designed and built by former MSE employee Adam Cable – lets you choose a handset model and colour, plus select the maximum you're prepared to pay upfront and what contract length you're willing to consider. It then shows you where's cheapest to buy the phone outright or with financing, and suggests the cheapest Sim-only deals for your chosen allowance.

Handily, it'll also let you know if there's a 24-month mobile contract with a cheaper average per-month cost available. The tool covers most networks, including piggybackers, and also lets you filter cashback deals by 'automatic' or 'redemption' (which are harder to claim).

For more help on cutting mobile costs, see our 30+ Cheap Mobile Tips.

What are the different ways to buy a new mobile?

There are essentially four ways to get a new phone (without stealing it – but don't do that). The MobilePhoneChecker tool checks prices via all four routes:

1. Buy it unlocked and pair with a Sim. This gives ultimate flexibility on tariff and is usually the cheapest way, but you have to stump up the dosh upfront (unless you buy the handset on a 0% credit card).

2. Get it on contract with a network. This saves on the upfront cost, but it generally costs much more over the lifetime of the contract than buying the handset yourself. See Mobile contract APRs.

3. Get it on contract from a reseller like Mobiles.co.uk* (owned by Carphone Warehouse). These are much cheaper than going direct to a network, and on certain tariffs can be unbeatable.

4. Buy it on finance and pair with a Sim. Get the cost of the handset loaned under a finance agreement over a fixed period.

This last one is a fairly new practice and only two companies in the UK do it specifically for mobiles, in partnership with peer-to-peer lenders:

• Mobile network Giffgaff (partnered with RateSetter) provides you a loan with a fixed APR of 18.8% (assuming you're accepted – you still undergo a credit search). At the same time you must order one of its Sims with the phone – though you only commit to a single one-month bundle and the handset comes unlocked so you're free to switch provider anytime.

• Newbie Unshackled.com (partnered with Zopa) differs in that you're loaned the cost of a handset on a personalised APR based on your own credit score – this can range from 9.7% to 24.9%. You're then free to choose a Sim-only deal with any provider you wish – this can be either a rolling one-month or 12-month contract.

New 'build your own contract' tool for mobile phones launches

So which is the cheapest way to get a new phone?

That's the big question. The very cheapest way depends on what phone you're after, how much you're able to pay upfront, how long you're willing to be locked into a contract and even, given the new peer-to-peer financing options, your credit history.

The tool's not perfect – for example it bases costs with Unshackled on its representative APR of 9.7%, when in fact you personally may get a worse rate. And, when letting you know that an equivalent handset contract may be cheaper, it doesn't link you to it – you have to manually go to the comparison page and re-enter your handset and usage details to find it.

However, the MobilePhoneChecker site, with the inclusion of this new 'Build your own' tool, is a good place to start to compare different options. To show the difference in price, we used it to look at the cost of buying a new 16GB iPhone 6s for a high user (at least 2,000 mins, 5,000 texts and 6GB of 4G data). Prices change regularly so always check.

Cost to get an iPhone 6s (16GB) on a high usage tariff

Here are the other key need-to-knows:

• The very cheapest deals are often available from third party sites that sell networks' contracts at cut-throat prices, such as Mobiles.co.uk*. On certain tariffs, this is actually cheaper than buying the handset yourself and pairing with a top drawer Sim – plus you also avoid paying the full whack upfront.

• However, these will be limited to a particular network and usage level that may not be appropriate for you. Additionally, you'll be stuck on a two-year contract and changing tariff will be costly – and once you reach the end of the contract you'll keep paying the same high monthly cost until you switch, so unless you're really on the ball it could cost you more in the long-run.

• Getting a 0% credit card and using it to pay for the phone yields a lower cost than going with a financing option – just make sure you only use it for this purpose, and be disciplined enough to pay it off each month. Unfortunately not all will be accepted for one.

See 30+ Cheap Mobile Tips, Cheap iPhones or Cheap Samsung phones for a full list of what to consider when looking for a new handset.