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Updated: 21 Apr 2022

Intel processors explained: What is Core i3, i5, i7, i9 and Pentium?

The most confusing part of buying a computer is the bewildering array of CPUs (also known as processors) on offer. Which? explains what you should be looking out for and what sort of processor is best for which task.
Michael Passingham
Intel core 473394

If you’re buying a computer, chances are it will have an Intel processor on board, although some come with AMD chips and newer Macs come with the M1 processor.

In this guide, we’ll explain what different Intel processor models mean and what sort of user they’re best suited for. This will help you to decide which intel processor you need and whether it's worth spending more money on a newer-generation processor.

You'll also be able to buy your next computer with confidence, as you'll be able to understand the jargon retailers and manufacturers use. Much of the information here can be applied to AMD Ryzen processors as well, particularly information on how to read model numbers, although the generational numbers we talk about do differ. 

Whatever your budget, our lab tests reveal which models are worth your money and which aren't. See our expert pick of the best laptops for 2022.

Intel processors: key terms you need to know

When looking at a processor, there are two main figures you’ll see time and time again. 

1. Clock speed

This measured in gigahertz (GHz, one billion hertz), and tells you how many operations a processor can do each second. The higher the number, the faster the computer (when comparing like-for-like laptop/desktop models). 

You’ll notice a higher clock speed when opening programs, files and exporting photos.

2. Number of cores 

Typically, laptop and desktop chips have two or four cores (known as dual-core and quad-core). Some newer models have six and even eight. The more cores, the better, because it allows your computer to run multiple tasks at the same time without slowing down. 

You’ll appreciate more cores if you often have lots of programs running or open lots of web browser tabs. 

However, comparing the number of cores between different types of Intel processor (such as comparing an Intel Atom with an Intel Core i5) won't tell you much; as the cores themselves are completely different. Four Atom cores are much less powerful than four i5 cores, for example.

Intel Atom – best avoided

Atom processors heralded the arrival of ultra-thin, ultra-light laptops in the mid-2000s. These chips offered four cores for sprightly everyday computing performance.

Nowadays, these chips are generally relegated to very cheap Windows tablets costing under £200. Since there haven't been any new Atom processors in years, we'd advise you steer clear of any devices using an Atom processor as they are now extremely slow.

Intel Celeron and Pentium – cheap laptops and very cheap desktops

Celeron and Pentium processors are at the very bottom of Intel’s range. You might be familiar with the Pentium brand, with the name being a mainstay of more powerful computers of the late 1990s. Nowadays, it sits just above Celeron in terms of performance.

Celeron processors have improved in recent years, but they rarely excel in our tests as they are too slow for anything but very basic tasks, and multi-tasking with multiple programs is almost completely out of the question. They're usable, but given there are much better processors available in laptops that aren't hugely more expensive, we don't think they're worth seeking out.

Newer Pentium models, such as those launched in 2017 onwards, are becoming more common on laptops costing between £250 and £300. These chips are power-efficient, meaning they’re great when you want a laptop with a long battery life. They’re perfectly usable for web browsing and basic office work.

See our pick of the best cheap laptops.

What's the difference between Intel Core i3, i5, i7 and i9?

Core i3 processors offer a great mix of price and performance. They aren't the best for heavy multi-tasking or more challenging tasks such as editing videos, but they offer a noticeable step up from Pentium processors without you having to spend too much more; you'll find them in laptops from about £350 and up.

Core i5 processors are a great choice if you want a computer that can perform lots of tasks at once, and perhaps even delve into photo and video editing work. They don't cost as much as i7 processors but they offer performance that isn't too far off. It's the specification we recommend to most people, and you can grab one in a laptop for about £500.

Core i7 is a step up from i5, with a bit of extra performance to make those tough tasks that bit quicker. You often pay a premium for this, and if you have no specific need for speed then you may well not need or want to pay the extra.

Core i9 chips are reserved for specialist computers working on extremely challenging tasks, usually editing large videos. These would be overkill for most people, although if you do get the chance to use one you'll surely notice the scintillating speed.

Want to complete your home office setup with a screen? Read our computer monitor reviews to find the best.

What do the numbers and letters at the end of Intel Core i processors mean?

This used to be an area of real confusion with Intel processors, and while it's far from plain sailing nowadays, it's a lot simpler than it used to be. The make-up of an Intel Core i chip model name can be broken up into five parts, each part giving you a little more information about the processor in your computer.

The first part is the easiest: Core i3, i5, i7 i9 are the processor's brand and tells you broadly where it fits into the range. Laptops and desktops with Core i3 are typically the cheapest and least powerful, with i5, i7 and i9 representing large steps up in performance. 

Within each range, there are three more elements to consider.

We'll take the the Intel Core i5-1145G7 as an example. 

Looking for a new computer? Our tough lab tests reveal which are worth your money - see our laptop reviews and our desktop PC reviews.

Part one: generational number

The first digit after the dash tells you which generation your processor is from. The higher the number, the newer it is. As of 2022, the latest generation is 12th gen, meaning all the model numbers from this generation start with the number 12, and our example above is from the 11th-generation, hence it starting with 11 (1145G7). Ninth-generation processors and earlier start with a single digit, rather than two. 

This is useful to know, as it can not only help you know the age of a laptop if you're buying used or refurbished, but it also lets you easily compare between two models. 

The newer the processor, the better performance you'll get for the money. But if two models of laptop have processors perhaps only one generation apart (9th gen vs 10th gen, for example), the difference between them will be pretty small, so if the 9th-gen model is substantially cheaper it could well be a better buy.

See our guide to buying used or refurbished laptops for more.

What are the generations of Intel processor?

Below are the years in which each generation of Intel Core processor was launched, plus the codename you'll sometimes see them referred to as.

Year first released
Number in model name
2nd2011Sandy Bridge2
3rd2012Ivy Bridge3
7th2016Kaby Lake7

Part two: Position in range

After the generation number, you get two digits (or three in post-10th-gen processors) that tell you roughly where in the hierarchy the processor sits. If you compared the two numbers in two processors, for example Core i5-1145G7 and 1140G7, you could glean that the 1145G7 was more powerful. However, Intel does not recommend you use these numbers for comparison as the 'bigger is better' mentality may not always hold true when comparing all processors as there are other technical differences that aren't apparent from these numbers.

Part three: Suffix

The suffix (trailing letters or letter and number) give you more information about where the processor sits in the range. Our suffix in our example is Core i5-1145G7,for example, but there are other variations including the i5-11300H and the 11600, which has no suffix at all. Below is a list of the common suffixes you'll find.

  • G and a number at the end: Processors from the 10th-generation onwards (models starting with, 10, 11 or 12) often end with a G and a number, for example, G1 or G7. The higher the number on the end, the better the built-in graphics chip on the processor will be. The product listing should provide more detail as to what sort of performance you can expect.
  • No suffix: This is a standard desktop processor, generally with four cores and a high clock speed for excellent everyday performance and the ability to edit videos and photos at high speed.
  • T suffix: Found in smaller desktops and all-in-one PCs. These chips are functionally the same as those without a suffix and have the same number of cores, but with a slower clock speed.
  • K suffix: The highest-performance processor you’ll find in a computer you can buy on the high street. Similar to a chip with no suffix, but generally with a higher clock speed. These chips can be ‘overclocked’ by those with technical knowledge.
  • U suffix (older chips only): ‘Ultra’ low power. These chips generally have two cores (although newer models now have four cores) and are among the slowest processors with Core i branding. These chips can often be found in cheaper AIO PCs and in many laptops. They can be suitable for photo and video editing, but tend to be a lot slower when performing tasks such as exporting files to disk. If you’re looking for a photo-editing machine, pick a Core i5 or even try to stretch to an i7.
  • HQ suffix: Generally found in powerful laptops and normally come with four cores. Perfect for video and photo editing, but sacrifices battery life and portability.
  • Y in the middle (older chips only): Y are the lowest-power chips you can find. They aren’t really suitable for photo or video editing but will be fine for lighter tasks. The advantage of choosing one of these is very good performance for lighter tasks, coupled with a longer battery life. Laptops that use this chip tend to have fanless designs, meaning they’re totally silent and very thin.

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