One great way to improve the performance on any Mac is to install more RAM. On older models this is actually a very simple procedure, and if you use third party RAM from companies such as Crucial you'll find the cost quite affordable too. Modern Macs are a different story. Of the current range there are only three models that can be manually upgraded. These are the 27" iMac (either the Retina or non-Retina models), the Mac Pro, and the non-Retina 13" MacBook Pro. For all other Macs Apple has chosen to solder the RAM, making it virtually impossible to remove. You can of course use the built to order feature on the Apple website to upgrade the RAM at point of purchase, and we recommend in some cases that you do this, as it may well extend the productive life of your Mac.

 As a general rule we would suggest that you have at least 8GB of RAM fitted in your Mac. For everyday tasks 4GB is perfectly fine, as internet browsing, running office software, and light gaming will work without issue. The only reason we advise upgrading to 8GB when you buy your Mac is the simple reason that you can't later on, and over time software tends to become more demanding. If you intend on using more advanced software such as Photoshop, or some video editing suites, then the extra RAM will prove very useful, and generally speaking it's always better in technology terms to have slightly more than you need rather than less. Power users who run virtualisation software would really want to look at the most RAM available for their system.

How to upgrade the RAM in a Mac: Using the Apple Store built to order feature.

If you want to upgrade your Mac when you buy it from Apple it's very easy to do so. After you've selected the model you wish to buy you'll be presented with a screen that asks you to configure your Mac. Scroll down to the Memory section and tick the box you want. Recently Apple has started to offer commonly requested configurations at the top of the page in the Get It Faster section. When we checked the memory upgrade was top of the list.

upgrade Mac RAM

How to upgrade the RAM in a Mac: Which MacBooks can be upgraded?

Across the laptop range, MacBooks are now pretty much unserviceable by the user. MacBook Airs all arrive with 4GB of RAM, which can be upgraded on the Apple Store to 8GB for £80, while the 13" MacBook Pros with Retina displays all start with 8GB, upgradeable to 16GB for £160, and the 15" models all come with the maximum 16GB already fitted.

The one exception is the old-style 13" MacBook Pro. Now, this machine remains a very customisable Mac, with the user being able to replace the battery, RAM,  and hard drive with little effort. The RAM slots are accessible by unscrewing and removing the bottom plate of the device, which reveals them in the centre of the machine. Just pop them up, remove the current chips, slide in the new ones, and your device is upgraded. This makes the non-Retina MacBook Pro a great choice for hobbyists or those who want to spread the cost of ownership across several years.

It's not quite that simple though.

While at first the prospect of a Mac you can fix yourself feels very attractive, you have to also bear in mind that this particular MacBook hasn't been updated for a couple of years now, and frankly it's a bit past its sell-by date. While the machine is perfectly usable, the innards are old by technology standards, and the 1280x800 resolution screen is a huge drawback when compared to the 13" MacBook Pro with Retina display that retails for only £100 more and comes with an SSD and 8GB of RAM. You can fix many things on the old MacBook, but sadly the screen isn't one of them.

Read: How to upgrade an old Mac - Create a FrankenMac!

How to upgrade the RAM in a Mac: How the Mac Mini has changed.

Up until late 2014 the Mac Mini was also a very easy device to upgrade yourself. Simply unscrew the plastic base and there were two pop-up RAM slots into which you could place new chips. If you have one of these models then it's probably fitted with 4GB of RAM, as that was the standard Apple issue. Today on memory chip retailer Crucial's website you can buy an 8GB kit for £61.19 or 16GB kit for £116.39, either of which would give the machine a performance boost, especially if you paired it with a new solid state drive.

Sadly the new 2014 Mac Mini no longer offers the manual upgrade feature of its predecessor, and if you want to increase the RAM it will need to be bought from Apple. The current entry level model has 4GB fitted, which can be increased to either 8GB for £80 or 16GB for £240. The two higher models both come with 8GB of RAM, which again can be increased to 16GB for £160.

How to upgrade the RAM in a Mac: Which iMacs can be upgraded?

It's a similar story on the iMac range, although the entry level 2014 iMac comes with 8GB fitted as standard and actually can't be upgraded any further, the other 21.5" models arrive with 8GB but have an option to upgrade to 16GB for £160. Again, if your needs are relatively light - i.e. you don't use your Mac for image editing, video production or heavy gaming - then the 8GB is more than likely enough. The new 27" iMacs come with 8GB fitted, but are fully capable of being upgraded by the user to a maximum of 32GB. Apple of course offer an upgrade service which costs £160 for 16GB and an eye-watering £480 for 32GB, but as you are free to source your own RAM you can visit Crucial and get the same capacities for £116.39 (16GB) or buy two to give you 32GB for £232.78, saving you nearly £250 when compared to Apple's prices.

How to: Install extra RAM in a 27-inch iMac

First buy the extra RAM, as described above to save money on Apple's exorbitant prices. You should find cheaper RAM memory for your Mac model at online retailers such as Crucial.

New iMac memory from Crucial

Turn off and unplug your 27-inch iMac (Late 2012 model).

Place it flat screen down on something soft (eg. a towel or blanket) to protect the screen.

27-inch iMac memory hatch door

Press the small button at the top of the power socket (shown above), and pick out the memory hatch door above it. This is quite possible to do using just ytour fingers. Try to avoid using something to help lever the door open as you might scratch your Mac. Get someone with longer, strong fingernails if that helps. You really don't need much pressure to open this door.

Open iMac memory hatch door

You'll now see the two 4GB memory DIMMs that Apple ships as standard with its iMacs.

Apple illustrates how the RAM should be fitted on the back of the memory hatch door.

27-inch iMac memory install DIMM instructions

27-inch iMac memory hatch door DIMM slots 1

Now pull out the little arms to raise the iMac RAM slots.

27-inch iMac memory hatch door DIMM slots 2

Now add your two new DIMMs in the empty slots. There's no need to remove the existing memory chips, unless you're adding four new 8GB DIMMs for the maximum 32GB memory installation.

27-inch iMac memory install DIMM slots 3

Press back the small levers so that the DIMMs are back flat.

27-inch iMac memory install DIMM slots 4

Put the door back on so that it clicks back into place. You don't need long fingernails for this!

27-inch iMac memory install DIMM door

That's it. You've just increased the performance of your 27in iMac for a fraction of the cost that Apple would prefer you paid it at the point of sale.

How to upgrade the RAM in a Mac: The Mac Pro

There are currently two versions of the Mac Pro - the Quad core and 6-core models. Both are upgradeable buy the user to a maximum of 64GB. The Quad-core model comes replete with 12GB, and Apple offer upgrades to 16 GB (£80), 32GB (£400), and 64 GB (£1040), while the 6-core starts with 16GB and has 32GB (£320) and 64 GB (£960) options. When we looked on Crucial for Mac Pro compatible EEC RAM the current prices were £303.59 for 32GB which translates to £607.18 for 64GB. Which means you could buy an iPad Air 2 with the money you'd save.

Fitting the RAM yourself is very easy. Simply slide off the outer case and inside you'll find the RAM slots fitted vertically on either side of the panel containing the USB and Thunderbolt ports. Press the button at the top of the slot marked with a white arrow and the RAM modules will pop out. Now remove them, put in your new ones, and you're done.