Most people would accept that modern Macs are fast; but how fast are they exactly? Is speed subjective - Craig Federighi's beloved but vague "buttery-smooth performance" - or can we assign objective values and compare one computer's speed against another? And what is the best way to compare the speed of two Apple machines, or a Mac against a Windows PC?

We can answer these questions with benchmarking: the use of a variety of (usually free) apps to evaluate a machine's performance (and more specifically, the performance of its individual components) in a range of scenarios. Carry on reading to find out how to benchmark the CPU, GPU and hard drive of your Mac desktop or laptop.

What's the point of speed-testing a Mac?

While it's hard to quantify general performance in technology, benchmarking provides numbers for comparison with other machines and devices. Simply put, benchmarking is a way to test out the performance of a piece of tech, whether the CPU of a smartphone or the GPU of a Mac.

Benchmarking can help you decide whether to upgrade to a new desktop or laptop, and help understand the performance of the various pieces of tech within, from the CPU to the GPU and even the hard drive. It can help identify weak spots in your system that can be enhanced, whether by adding more RAM or upgrading to an SSD. (Here are some more tips for speeding up a slow Mac.)

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General performance benchmarking

While there are many general benchmarking apps available for macOS, the easiest to use and most widely recommended is Primate Labs' Geekbench 4 (£9.99/$9.99). It's our go-to benchmark when reviewing the latest iPhones and iPads here at Macworld UK.

Why? While the paid-for version linked above has more features, Geekbench 4 is also available in a free Tryout version. And the software works across multiple platforms including Windows, macOS, iOS and Android. 

There aren't many limitations to the free version of GB4, apart from that it requires an active internet connection at all times and will automatically upload the results to its website for others to see. As long as you're not benchmarking an unreleased Mac while under embargo, it should be okay to share the results with other Geekbench users.

Anyway, the main draw of Geekbench 4 is that it's incredibly easy to use and requires little technical knowledge. Simply open the app, close any other apps that might be running on your Mac and click 'Run CPU benchmark'.

It'll then measure the performance of your CPU when performing "everyday tasks designed to simulate real-world applications" and can take up to 20 minutes to complete, depending on the speed of your CPU.

How to test a Mac's speed: Geekbench 4

Once it's done, the results will be displayed in your preferred web browser. Yes, you might initially be overwhelmed by all the information on offer, from the Processor ID to the Motherboard hardware, but the only two numbers you need to concentrate on are at the top: single-core score and multi-core score.

The single-core score helps give a sense of how fast the Mac performs under certain situations when only a single processing core is handling everything. Multi-core, on the other hand, shows you how well your Mac can perform when pushed to its absolute limits, as it'll use multiple processing cores at once to handle the strain. Think of it as your Mac's top-end performance.

You can take these results and compare them to other benchmark tests on the Geekbench Browser, allowing you to see how your Mac compares to the latest generation of Macs, and even its competitors from other manufacturers. It should give you an idea of how well your computer is performing at the moment, and whether the upgrade you're considering is worth it in terms of raw processing power.

Hard drive and SSD benchmarking

When it comes to measuring the read/write speeds of your hard drive or solid state drive, the easiest tool to use is BlackMagic Disk Speed Test (free). Although it was designed for video editors to help determine whether their hard drives can handle large files, it's extremely easy to use.

Simply download and open the app, select your target drive if your Mac has more than one hard drive (this is done by clicking the gear cog) and click start to begin the benchmark. For improved accuracy, and as with all other benchmark tests, it's best to make sure that no other apps are running at the same time.

How to test a Mac's speed: BlackMagic Disk Speed Test

While there's a bunch of data showcased in the Will it Work? and How Fast? charts, that's mainly for video editors. The numbers you want to focus on are displayed in the big gauges at the top. The write speed is on the left and the read speed on the right, giving you an idea of how fast things will be written to the drive and how fast apps and files will load respectively.

What's a good score?

While a standard external hard drive connected to a Mac via USB 2.0 won't reach speeds of more than 25-30MB/s (extremely slow), upgrading your built-in hard drive to an SSD should see significant gains in performance. Take our 2011 iMac, for example: while the built-in hard drive reaches speeds of up to 90MB/s, our external SSD connected via Thunderbolt achieves up to 420MB/s.

The difference in speed is dramatic, and is immediately noticeable in everyday use. In fact, it's probably the main reason that Apple has replaced traditional hard drives with solid state drives across its entire MacBook range. If you've got a slow hard drive, it might be looking into upgrading to an SSD.

Graphical benchmarking

Finally, let's talk about graphical performance. For this, we usually opt for Maxon's Cinebench, another free piece of software that, in addition to testing your Mac's CPU (much like Geekbench without the ability to compare with other results online), will use an OpenGL test to benchmark your graphics card.

The test uses 3D cars interacting in a dimly lit city street to test how your GPU handles nearly a million polygons at once when combined with several special effects.

How to test a Mac's speed: Cinebench

To perform the test, simply open Cinebench and click Run next to the OpenGL test in the top-lefthand corner of the app. It'll take you through the test, and your final result will be displayed next to the Run button.

What's a good score?

Our 2011 iMac managed only 42.66fps in the benchmark, but newer Macs, including the top-end Mac Pro, can hit speeds of around 77fps.

Traditionally, Macs aren't as powerful as their PC counterparts in the graphics department thanks to a lack of high-end nVidia/AMD processors in Macs, and this should be taken into consideration when benchmarking and comparing results with PCs. Unlike with other components, the graphics card can't be upgraded on most Macs; if you're looking for better graphical performance from your machine, you'll probably need to pay for a newer Mac.

If you do end up looking for a new Mac, take a look at our Mac buying guide.