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How we test mobile phones

By Oli McKean

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

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We independently test more than 40 smartphones every year to find the very best models on the market. But how exactly do we test them and what does it take for a smartphone to be made a Best Buy in our lab tests?

Jump straight to:

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 74% based on its performance in our lab is made a Best Buy, which means that it has our recommendation. 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 – their battery doesn’t last long enough after charging, they produce poor-quality pictures and are difficult to use. 

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 completely. 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 scratch resistance. Behind each of those ratings includes more than 20 individual tests and checks that are weighted differently. This means that the most important things, such as how long you’ll have to browse the internet on your phone before it goes flat, will more greatly impact the score than features such as how easy it is to use the phone’s music player application. 

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

Our key testing criteria

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

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 can withstand usage 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 run two key battery tests on every mobile phone – making continuous calls and browsing the web. We charge each mobile phone to full battery for each test, and assess how long it lasts to reach flat with each task. 

We perform identical tests again, but after a shorter charge of 15 minutes to see how well each phone would withstand usage after with a small burst of power. 

We also check how long each phone takes to reach full and 15-minutes charge, so you know whether the phone charges quickly or needs extra time to get enough power.

Battery makes up 25% of the 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, including the sensitivity of the screen to how easy it is to navigate the phone’s operating system. 

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

Ease of use makes up 15% of the score.

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 nine different shooting environments, from indoor close-up shots to outdoor landscape shots, and measure them against a variety of criteria.

We look at how well phone’s do the basics such as deliver good overall picture quality all the way up to slightly more advanced qualities, such as producing good flash uniformity and colour accuracy. 

Our test scenes feature a weird and wonderful range of objects, from a fluffy teddy bear to a wicker chair. These are used so our experts can assess whether the camera picks up texture and subtle detail.

As well as evaluating a phone’s front camera, taking photos is only one half of how well a camera performs. We also look at how well a phone captures videos, so you know whether your phone will capture clips with the same high quality as its videos.

Camera makes up 15% of the score. 

Mobile phone call sound quality 

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, as well as with a noisy café soundtrack in the background, to simulate how well it would deal with disruptive background noise.

We play the café track at 74dB – that’s somewhere between the level of the average alarm clock and normal street 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. 

Call clarity makes up 10% of the score.

Mobile phone speed and responsiveness  

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 and how responsive it is when faced with real-world ‘heavy’ tasks. We benchmark the speed of each phone’s processor, and also put them through a series of lag-worthy tasks to see how well they hold up. These tasks range from playing resource-intensive games to opening large PDF files.

Processor makes up 10% of the score. 

Mobile phone screen quality 

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

Here, we put every phone through multiple scenarios to evaluate the quality of its display. This involves looking at phone in standard and demanding lighting conditions. 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. 

Screen quality makes up 10% of the score.

Mobile phone music and video 

Key question: How well do the music and video applications on the mobile phone work?

This score is made up of testing the quality of media applications on every phone. Audio testing involves using six reference tracks of varying speeds, genres and pitches, and video requires testing the experience of making video calls from how long it takes to make the call to how good the audio-visual synchronization is. 

We use a control set of headphones so that audio is measured in the same way for every handset, but also test the sound against any headphones that are provided. 

Music and video makes up 10% of the score.

Mobile phone design 

Key question: Is this mobile phone built to last or is it cheap and flimsy?

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

It’s easy for a phone to look good on a website or in a video when a manufacturer captures the perfect angles, but our expert lab technicians assess everything on the phone, looking at how well it's designed to the durability of its materials, to make sure you’re buying a phone that lasts. 

Testing the durability of the mobile phones includes the quality of its display, to make sure it doesn’t just look good, but can also withstand conditions such as heavy scratching from a key if it’s chucked in your bag. 

Design makes up 5% of the 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.

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


 

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