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Updated: 29 Apr 2022

How we test mobile phones

Find out more about our mobile phone tests, and why you can trust our independent reviews to unearth the best models on the market
Alice Williams

We independently test more than 65 smartphones every year to find the very best models on the market. But what does it take for a smartphone to be made a Best Buy in our lab tests and what sorts of issues cause a phone to be given a dreaded Don't Buy? Find out why you can trust Which? reviews for your next purchase.

Why our mobile phones tests are different

Most free mobile phone reviewers make their judgement based on their individual experience of using a phone and produce a score that reflects their preferences. These reviewers typically receive samples directly from manufacturers or their PR representatives.

While we also occasionally do hands-on first look reviews to give you our personal experience of using a phone, the Which? overall score is generated solely from ratings and results that we receive from our independent lab where these phones are tested under identical conditions, so they're directly comparable. We also purchase every phone we test ourselves, so you can trust that there is no bias in our scores.

What are Which? Best Buys and Don't Buys?

The stakes are high for mobile phones, so we only give our Best Buy recommendation to the very best models on the market. A mobile phone that scores more than 71% based on its performance in our lab is made a Best Buy. That said, Best Buy phones aren’t perfect, so it’s still important to read our review to find out what weaknesses each phone has. On the other end of the spectrum, a mobile phone that scores 45% or lower is a Don’t Buy.

  • Best Buy mobile phones typically earn their score by delivering in the most important areas – an enduring battery that also lasts well on a short charge, excellent camera quality, and features and functionality that make it easy to use. 

  • Don’t Buy mobile phones struggle to do the core tasks well – the battery may not last long enough, pictures could be poor quality, it could be difficult to use or a combination of all three. 

How is the Which? score calculated?

The Which? overall score is a percentage. This score only takes into account the results of our tests and ignores price. All mobile phones are tested in the same way and on exactly the same scale, so you can compare any mobile phone at any price and know how it measures up against its rivals. 

Weightings and star ratings

A Which? overall score is made up by testing various criteria, from key ratings such as battery life, camera performance, ease of use, audio quality and durability. Behind each of those ratings includes more than 40 individual tests and checks that are weighted differently. This means that the most important things, such as the quality of your pictures and videos, will more greatly impact the score than features such as how easy it is to use the phone’s music player. 

To keep things simple, the most important scores are shown as star ratings out of five on each phone’s Test Results page, as an easy-to-compare list of strengths and weaknesses, so you can quickly work out whether a model is right for you.

How the overall mobile phone test score is calculated

  • Camera - 20%
  • Battery - 15% 
  • Display - 15%
  • Ease of use - 10%
  • Performance - 10%
  • Sound quality - 10%
  • Durability - 10%
  • Phone functionalities: 5%
  • Capabilities - 3%
  • Security - 2%

Our key testing criteria

Below are the key testing categories and how we evaluate each one:

Mobile phone camera quality

Key question: Will this mobile phone be able to capture the perfect shot?

This is a particularly technical test, as camera quality can vary hugely depending on the environment that the phone is in. That’s why we test every handset in 10 different shooting environments and measure them against a variety of criteria. 

We use mannequins of different skin shades to see how well the camera picks up all skin tones, and shoot different objects to see how well the camera picks up texture and detail.

We look at how well phones do the basics, such as deliver good overall picture quality, all the way up to more advanced features such as producing good flash uniformity and colour accuracy. We also take into account how the different lenses perform, as well as the speed of the shutter, and quality of the zoom and auto focus features.

Taking photos is only one part of how well a camera performs. We also look at how well a phone captures videos, and how well the image stabiliser works, so you know whether your phone will capture clips with the same high quality as its videos.

Camera makes up 20% of the overall score.

Mobile phone battery performance

Key question: How long does this mobile phone’s battery last?

One of the most important tests of a smartphone is how well its battery lasts after it’s been fully charged. It’s customary for manufacturers to make tall claims about how well a phone’s battery performs and our tests uncover whether they're true or not.

We use a robotic arm to interact with each phone until the battery runs flat. It's designed to mimic how you use your phone, watching videos, making phone calls, using the camera and navigating through a map app. We measure how long the battery lasts to see how well the phone can keep up with your typical day.

We also check how long each phone takes to reach full charge as well as the battery percentage after 15 minutes of charging, so you know whether the phone charges quickly in a pinch.

Battery makes up 15% of the overall score.

Mobile display

Key question: Is the mobile phone’s display good enough to survive any lighting conditions? 

We put every phone through multiple scenarios to evaluate the quality of its display, by assessing it in standard and demanding lighting conditions, using microscopes to assess sharpness and resolution.

Each phone is confronted with challenging situations, including low-light environments with high reflection to simulate what you’d experience on a train or any other area with frequently changing lighting. 

We also check how quickly a touchscreen responds to make sure it can keep up with all your texting and browsing.

Screen quality makes up 15% of the overall score.

Mobile phone ease of use

Key question: Is this phone easy to handle and navigate when you’re using it? 

Our lab technicians use their years of experience to scrutinise various features of how a phone is used from general usage to how sensitive the screen is.

Important factors such as how good a phone’s security features are also come into the ease-of-use rating, but we still take the fine details of a phone's functionality into account, such as how easy it is to view large amounts of texts on the default internet browser. This means you won’t be stuck with an expensive phone that’s a pain to use. 

Ease of use makes up 10% of the overall score.

Mobile phone performance

Key question: Will this mobile phone struggle and lag with tasks such as loading heavy web pages?

No one wants their phone to spend ages loading just to show an internet webpage. It’s important for your phone to be able to keep up to speed when you’re using it, so we test each handset to see how quick its processor is. We benchmark the speed of each phone’s processor and also put them through a series of day-to-day tasks to see how well they hold up.

Performance makes up 10% of the overall score. 

Mobile phone sound quality

Key question: How does music sound through the phone?

If you rely on your phone's audio to get you through a long journey, you want to make sure the sound is up to scratch. We play a range of tracks from from classical to R&B to make sure that your favourite music sounds crystal clear.

Key question: Do calls on this mobile phone sound loud and clear?

Here, we test how good the quality of phone calls are on a mobile phone, making calls to and from the phone to evaluate how well it copes in different environments.

Like many of our other tests, we don’t just test the phones in one environment. We test them in a normal, quiet lab setting, and check how well it would deal with disruptive background noise. We listen to see whether you and the person on the other end of the line can be understood clearly, how well the noise cancelling works and if there is a good level of volume.

Sound makes up 10% of the overall score.

Mobile phone durability

Key question: Is this mobile phone built to last?

Here, we round off our testing by looking at the fundamentals: what is the build quality of this phone?

Our expert lab technicians assessments go beneath the surface, to make sure you’re buying a phone that lasts. Testing the durability of the mobile phones includes the quality of its display and to make sure it can also withstand conditions such as heavy scratching from a key if it’s chucked in your bag. 

We also check how well a phone would survive being rained on. And if the manufacturer claims it's waterproof, we submerge it in water, just to make sure.

Durability makes up 10% of the overall score.

Mobile phone security

Key question: Does this phone keep your data safe?

Your phone knows more about you than most, so you want to be confident that it keeps this information safe. We put each phone through our security tests to see how well it guards your data.

We also check phones regularly for security updates – crucial software that keeps your phone secure. If manufacturers stop updating older phones, we remove any Best Buys.

Security makes up 2% of the overall score.

Find the right mobile phone for you with Which? reviews

We’ve tested mobile phones from more than 22 brands, so whether you’re a Samsung loyalist or you want to explore models from emerging brands such as Oppo or Realme, we’ll give our impartial view on whether your next purchase is worth your money. 

From the table below, you can see that we’ve tested phones at price point – budget, mid-range and premium. While premium phones typically get higher scores, we have found some incredibly good phones that cost as much as a third of the price but are still Best Buys. 

PriceLowest scoreHighest scoreAverage
Less than £30021%69%56%

Based on 233 mobile phone reviews on which.co.uk in April 2022.

Check out our mobile phone reviews to find the phone that suits you.