The Complete Guide to RAM Speeds
All the information and picks needed to find the best choice for your build
When you’re looking to build your PC and you’ve arrived at selecting RAM, it can feel overwhelming to know the right GB, MHz, and CL measurements for your needs.
This is why today’s What in Tech feature will be taking you through everything you need to know about RAM, from common speed versus speed questions and which spec matters most in your decision.
We’ve also included the best RAM choices available with different budgets in mind.
This is a long guide, the contents table below is your friend! Look specifically for the questions & recommendations that interest you instead of reading top to bottom!
Table of Contents
What is RAM Speed?
For the average PC builder, the capability of Random Access Memory (RAM) is measured by 3 key fundamentals: frequency, latency, and size (technically, size isn’t speed-related – but for the purpose of establishing what RAM is best for you, we’ll be covering it).
RAM Capacity / Size
RAM size is, as the name suggests, the overall capacity of the memory you’re buying. 4GB, 8GB, 16GB, and 32GB are the most common sizes right now.
Additional capacity means your PC will have the ability to run more programs simultaneously/switch between them more smoothly.
This is where the name “Random Access Memory” comes in. Your main storage (Solid State Drives, Hard Drives, etc.) are designed to offer much larger storage but are slower than RAM, which is why those drives are store your data and require a more significant loading time when opening them for use.
Once software/games/files are open, they then utilize your PC’s RAM, which is faster than your SSDs/HDDs, so that they can be “randomly accessed” quickly during use.
A common metaphor to explain the difference is that RAM size is almost like your desk, and the more capacity you have, the larger your desk is (meaning you can have more items in arms reach ready to quickly use).
While your hard/solid-state drives are the size of your shelves, drawers, and cabinets; these are used to store most of your items and take a little longer to take out for use on your desk.
Generally more RAM capacity is better, but there are diminishing returns (we’ll get back to that).
RAM Clock Speed / Frequency
Clock speed or frequency is a RAM’s MHz rating (nowadays, most RAM will be in the 2400Mhz to 4400MHz range).
Faster clock speed allows your processor to retrieve data located on your storage drives more quickly. Reducing the time it takes the CPU to access this data increases your performance in real-world scenarios and games.
Clock speed is measured in Megahertz (MHz) which indicates how many times per second your RAM can access its memory (as you probably expect, more is better, but we’ll speak further below about the sweet spot between price and utility).
CAS Latency
The last key part of the equation is Column Access Strobe or CAS latency (often just “CL”) which is integral in understanding RAM speed and often overlooked compared to a stick’s MHz rating.
CL indicates how long it takes your RAM to recognize a command/action (similar to how a monitor has latency between receiving your mouse click and outputting the result visually).
The latency is usually recorded by 4 numbers in the following format: 16-18-19-30 which represents the number of clock cycles it takes for the RAM to register a command. It is the first number from the 4 that is typically used to establish CL. Nearly all popular RAM today is between CL 12 & CL 18 (mostly CL14-16).
We talk more about how to balance latency and clock speed below. But to demonstrate why both are important, think about it: if you have very fast RAM, but the latency is high, it would be like gaming on a high-refresh-rate monitor but each of your actions takes a second to register (a dramatic example, but you get the point…).
How much does RAM Speed Matter?
So, we’ve established at a high level what the integral parts of RAM are for your build.
But how much does RAM speed matter?
The short answer is that for business and personal use (web browsing, e-mails, basic software, Netflix, etc), you’ll likely be fine with any 8GB (ideally 16GB) RAM from a reputable manufacturer.
If you’re into gaming or plan on using your build for production work like video editing, game development, or rendering, then the speed can have a more notable impact.
How much does size matter for RAM – 4GB vs 8GB vs 16GB vs 32GB
Of all the specs, size matters the most.
So if your battle is faster RAM vs more RAM (i.e. CL / MHz vs GB), we’ll nearly always recommend the latter option.
That said, RAM size does have diminishing returns. 16GB is what we recommend for nearly all users, 8GB for tighter budgets, and 32GB for high-end enthusiasts. Beyond that, there isn’t really much use (even 32GB is pushing past the realm of necessity unless you’re doing production work). If this sounds confusing, we detail the best RAM options towards the bottom of this guide.
How much does RAM clock speed matter?
Clock speed matters, but not as much as you may think.
You can build a powerful gaming PC with 16GB 2400MHz DDR4 RAM for instance (which is on the lower side of clock speed). Would it be better to have say, that 16GB of RAM at 3200MHz+? Absolutely! But it’s not a deal-breaker to have lower speeds if your budget is tight or you’re simply not bothered about fine-tuning potential performance/game FPS.
If you’re building a PC purely for basic business and personal use, we would suggest that cheap RAM will suffice for you as long as the size is large enough.
We do however see lots of unanswered questions from users around the difference between X MHz and Y MHz RAM. Which is why further below, you’ll find our comparison list as a quick guide to help you decide between two types of memory.
How much does latency matter for RAM
The most overlooked RAM speed factor, CL, is kind of like clock speed; it matters, but shouldn’t be a huge deciding factor in your PC building decisions.
A higher latency RAM (say, CL18) could still be perfectly decent if its other specs were around 16GB/3200MHz, RAM size is still the most important thing overall.
That isn’t to say that if you see CL12-CL14 RAM, you shouldn’t absolutely go for it if the other specs are decent (especially if you’re building a gaming PC or something for production work). But in the context of price/value, these low latency sticks are often 30%+ more expensive, which we can’t say is worth it unless you are trying to build the all-around most powerful computer possible.
RAM Speed Comparison FAQ
DDR3 vs DDR 4 – How much faster is DDR4
DDR4 is essentially the next natural iteration from DDR3. With significantly great size capacity & higher clock speeds, 4 is notably faster in nearly every case (latency is slightly higher on 4, but is made up for with the other specs).
In nearly all cases today, we would say pick up DDR4 RAM. It is overwhelmingly what the current market motherboards/CPUs are best compatible with.
The right question isn’t really “is DDR4 worth it” anymore in terms of speed. Because of its widespread market adoption, prices on this RAM are great. You’ll typically be getting faster RAM with little consequence compared to DDR3.
The only scenario we see DDR3 as worthwhile today is if you’re building an ultra-cheap PC and have specifically found a motherboard/CPU combo that supports 3 and not 4 (we don’t like this from a future-proof perspective and would try to stick to 4, but it could make sense if you need to be as cheap as possible).
DDR4 vs DDR5 RAM?
DDR5 RAM is in development and will offer 50-100% higher clock speed than DDR4, a slightly lower voltage and individual RAM sticks that can go up to 64GB each (the max with DDR4 is 16GB).
This sounds great on paper. But at this time, these ultra-high clock speeds/sizes lead to huge diminishing returns in pretty much all PC activity (we talk more about this in our comparison of higher MHz RAMs further below) so in reality, that 50-100% “theoretical” performance increase may not be super noticeable unless you’re building a very high-end machine (and in nearly all cases, the money would be better spent on a better CPU/GPU).
DDR5 RAM is scheduled for mass release in 2021. Though we recommend keeping expectations measured, as the DDR5 release date has been a moving goalpost for a couple of years now.
And even when the RAM is released, you can still expect a long-delayed period where motherboards, CPUs, and other PC hardware manufacturers take time developing new products that adopt DDR5 as the standard and take advantage of its speeds.
To sum up, while the difference between DDR4 and DDR5 RAM sounds exciting, we really don’t think it’s relevant to builders for the next few years. Stick to DDR4 for now.
What RAM Speed should I get?
The million-dollar question! Unfortunately, the answer isn’t clear-cut, as it depends on your budget and requirements.
A reasonable rule of thumb is to commit to at least 16GB RAM size-wise. Then from there, try to aim for a balance between CL/MHz between CL14 2666MHz & CL16 3200MHz.
To make it easier for you, the bottom of this guide details the best RAM picks today. If you want more autonomy on your choice, we’ve built the RAM speed quick-reference list further below too.
More RAM vs Faster RAM (Size vs MHz/Latency)
We’ve touched on this already, but it’s worth re-iterating: size is way more important than MHz & latency for nearly all users.
As an example, 2400MHz 16GB RAM will be better than 3200MHz 8GB RAM. The only time we’d pick MHz/latency improvements in this kind of bracket is if your remaining budget can’t jump up to a larger size, but could be squeezed slightly further to accommodate faster sticks.
The other exception to this rule is if you’re buying very large RAM. If you have 32GB in memory, we can’t imagine more will be required for a long time (unless you’re creating a very high-end production machine). At this point, if you still have the budget, it will be usually better to focus on faster 32GB RAM than slower 64GB+ memory.
MHz vs Latency – which is more important for RAM speed?
The difference between MHz and CAS latency value is a difficult question as the best approach is for there to be a balance between these 2 factors (instead of very fast frequency/slow latency or vice versa).
The “sweet spot” for most users today (particularly gamers) with the price in mind is around CL14 2666MHz to CL16 3200MHz.
Now you can fall outside of these balances (e.g. plenty of RAM sticks offer CL18 latency but make up for it with significantly more frequency or lower prices) but we would use that range as the rough spot to go in unless you’re building something high-end and are trying to get extra-low latency and high MHz.
RAM Speed Importance for Intel vs AMD
The main function of RAM speed is to empower your CPU and its ability to retrieve/store randomly accessible data easily.
So your CPU is indirectly an important factor in deciding how much to invest in RAM speed. For example, if you’re buying a high-end CPU, you’ll achieve more value from spending extra on fast RAM (as lower speeds can bottleneck certain CPU operations).
When it comes to the Intel vs AMD builds, it’s complex as the impact on speed depends on the chipset & model version. But as a (mostly reliable) rule of thumb: AMD CPUs/builds benefit more from better RAM speeds than Intel due to the way its memory controllers operate.
This is not to say RAM speed doesn’t matter for Intel CPUs however. We’ve seen many RAM benchmarks show games and various software processes perform notably better with higher frequency/lower latency memory on Intel chipsets.
CL 12 vs CL 13 vs CL 14 vs CL 15 vs CL 16 vs CL 17 vs CL 18
Our comparison list just below focuses on the difference between MHz as we often see reader questions specifically asking about the frequency differences.
But as made clear in this guide, latency is as important as the frequency in deciding RAM speed.
For example, the difference between CL14 and CL16 is usually more significant than the difference between 3000MHz and 3200MHz. But focussing all on latency (or all on clock speed) introduces diminishing returns, which is why considering both factors is important.
Unfortunately, it’s not a simple balancing act between the two measurements, as you’ll often see companies sacrifice low latency for high speed, or charge a lot more to ensure both specs are good.
We’ve detailed some of the best RAM available today at the bottom of this guide to make it easier for you. But if you do want to decide yourself, we would try to stick to the previously mentioned “sweet spot” of between CL14 2666MHz to CL16 3200MHz for mid-range builds, or you can seek faster/lower latency sticks if you have the budget.
