If you're wondering whether you need a Core i5 processor or can get away with a cheaper Core i3 we'll explain the differences and help you to make a decision.

These days, even a basic dual-core processor is fast enough for undemanding tasks. This means that whether you're buying a laptop or a PC, Windows should run perfectly well on even a budget model.

Undemanding tasks are just about everything bar gaming, video editing. (If you do want to do these, see our guide to the best processor for gaming and video editing.

Essentially, if you just want to do all the normal things people do with their computers - email, web browsing, YouTube, editing and sharing photos, Microsoft Office - a basic processor is fine.

If you're reading this during the process of trying to choose a budget laptop, know that one of the most influential components for overall responsiveness is the hard drive. It's worth sacrificing a Core i5 processor for an i3 if you can get an SSD instead of a traditional hard disk for the same sort of price.

Check out our list of the best cheap laptops and buying advice, too.

How many cores do I need?

You rarely, if ever, see single-core processors any more and you should avoid these at all costs. More cores means more performance, plus the ability to run multiple applications at the same time.

Many programs can also take advantage of multiple cores so even if you're only running that one program, you should see an improvement in its performance compared with running it on a computer whose CPU has fewer cores.

Hyper-Threading

Don't just look at the number of cores, though. Intel processors often support Hyper-threading which effectively allows it to handle twice the number of 'threads' and is a bit like having double the number of cores, albeit virtually. 

A thread in computing terms is a sequence of programmed instructions that the CPU has to process. If a CPU has one core, it can process only one thread at once, so can only do one thing at once. It's actually more complex than this, but the aim here is to keep it simple and understandable.

Hence, a dual-core CPU can process two threads at once, a quad-core four threads at once. That's twice or four times the work in the same amount of time.

Hyper-Threading is a clever way to let a single core handle multiple threads.

A Core i3 with Hyper-Threading can process two threads per core which means a total of four threads can run simultaneously. The current Core i5 range of desktop processors doesn't have Hyper-Threading so can also only process four cores. i7 processors do have it, so can process eight threads at once. Combine that with 8MB of cache and Turbo Boost (below), and you can see why Core i7 chips are more powerful than an i5 or i3.

Turbo Boost

Turbo Boost is Intel's marketing name for the technology that allows a processor to increase its core clock speed whenever the need arises. The maximum amount that Turbo Boost can raise clock speed depends on the number of active cores, the estimated current consumption, the estimated power consumption, and the processor temperature.

Core i3 processors don't have Turbo Boost, but i5 and i7s do. It means that Core i3 chips tend to have quite high 'base' clock speeds.

If a processor model ends with a K, it means it is unlocked and can be 'overclocked'. This means you can force the CPU to run at a higher speed than its base speed all the time for better performance.

A dual-core processor running at a faster speed than a quad-core processor could have similar performance overall.

7th generation Core i5 processors

Here's the current range of 7th generation Intel Core i5 chips for desktop PCs. These have the codename Kaby Lake. They're all quad-core CPUs, but don't support Hyper-threading:

Model

Core i5-7600K

Core i5-7600

Core i5-7500

Core i5-7400

Price

£239

£219

£199

£189

TDP

91W

65W

65W

65W

Cores/Threads

4/4

4/4

4/4

4/4

Base Frequency

3.8GHz

3.5GHz

3.4GHz

3.0GHz

Boost Frequency

4.2GHz

4.1GHz

3.8GHz

3.5GHz

Unlocked

Yes

No

No

No

Graphics

Intel HD Graphics 630

Intel HD Graphics 630

Intel HD Graphics 630

Intel HD Graphics 630

Smart Cache

6MB

6MB

6MB

6MB

View the Intel Core i5 Kaby Lake processors on Amazon here.

7th generation Core i3 processors

And here's the range of Core i3 desktop processors. These are dual-core but do support Hyper-threading. They don't have a boost frequency, but run at fairly high base frequencies.

Model

Core i3-7350K

Core i3-7320

Core i3-7300

Core i3-7100

Price

£185

£159

£149

£119

TDP

60W

51W

51W

51W

Cores/Threads

2/4

2/4

2/4

2/4

Base Frequency

4.2GHz

4.1GHz

4.0GHz

3.9GHz

Boost Frequency

N/A

N/A

N/A

N/A

Unlocked

Yes

No

No

No

Graphics

Intel HD Graphics 630

Intel HD Graphics 630

Intel HD Graphics 630

Intel HD Graphics 630

Smart Cache

4MB

4MB

4MB

3MB

View the Intel Core i3 Kaby Lake processors on Overclockers UK here

Confusingly, the 7th generation laptop processors don't follow this pattern. There are a couple of Core i5 models (the 7300HQ and 7440HQ) which are quad-core without Hyper-threading, but the rest are dual-core chips with Hyper-threading.

The three Core i3 models are also two-core, four-thread CPUs, but as with the desktop versions, have no boost mode.

Most cheap laptops, however, have slightly older Intel chips from either the 6th generation or earlier. You can easily tell which generation a chip is from by the first number in the model name. So a Core i5-6200U is a 6th-gen chip.

What about graphics?

Many Intel processors have a GPU - the graphics chip - built into the CPU.

6th-generation (Skylake) Core i3 and i5 processors have built-in HD Graphics 530, while the 7th generation have 630 GPUs as you can see from the tables above. The Core i7-7700, 7700K and 7700T also have this GPU.

However, while it's ok for casual games, enthusiats will still want to have a separate graphics card (see our list of the best graphics cards) to run demanding games at high resolutions and levels of detail.

Which is best: i3, i5 or i7?

You'd be forgiven for being confused at this point. It's not possible to look at a processor's specifications and make a decision about which is fast enough for you. 

That's why we rigorously benchmark every laptop and PC we review. This tests the whole-system performance, not just the CPU. It's the processor, plus the memory (RAM) and hard drive - along with the graphics card, too - which determines how quick a PC or laptop is.

So it's crucial to read reviews before you buy one. Here are the best laptops you can buy right now and also the best PCs.

There are other factors besides performance, such as amount of power a processor uses. Newer processors are generally always more power efficient, which is important in laptops.

You either get more battery life for the same performance, or more performance for the same battery life.

But to answer the question, a top-of-the-range Core i5 is going to offer the best performance than any Core i3, but a top-of-the-range Core i3 could be enough for you compared to the slowest Core i5 from the same generation.

Similarly, if you're going to be running very demanding software such as video editing or encoding programs, then you may want to go for a Core i7. But for most people, this is overkill.

If you're after the best battery life, look for a processor with a model number ending in U, or with a Y in it. These use the least power, but also deliver slower performance.

Finally, don't forget AMD. It's new range of Ryzen processors for PCs are excellent value and the Ryzen 5 chips are better value than Intel's Core i5.