Before you read the table of HSFs below, please keep in mind the following points:

• The budget, mid-tier, and high-end columns are for air-cooling. Closed-loop-coolers (CLCs), or liquid coolers, use water to cool the CPU instead of air.
• Spending more money will get you better cooling and quieter operation.
• If your budget is constrained, you can always stick with the stock HSF, and buy an aftermarket cooler later when you have the money.
• If you're not overclocking, stock HSFs are fine. If your CPU runs warm, stock HSFs tend to get loud because the fans spin faster.
• Stock HSFs are sometimes simpler to install. Aftermarket HSFs usually include screws and other small parts.
• CLCs are divided into three categories: small (120/140 mm units), medium (240 mm units), and large (280/360 mm units). Here are examples of small and medium options: 

• 120mm CLC units perform somewhere between mid-tier and high-end air coolers, but they are often priced as high as the high-end. They offer less value, but take up much less space.
• Liquid coolers at 240+ mm compete with high-end air HSFs, and can be superior in cooling and noise levels. However, they are very expensive, and do not fit in all cases. Never buy a medium or large liquid cooling unit until you have made sure that you can install it in your case.
• Many CLC units are made by the same manufacturer (Asetek), with the main difference being the type of fans that are used.

CPU coolers work by drawing heat away from the CPU through direct contact with the metal of the chip achieved via a thin layer of thermal paste. They then use fans to move room-temperature air past the area of the cooler that has gathered the heat (usually an array of metal fins, metal heatpipes, or a radiator with liquid running through it). Finally, as the fans continue blowing, the heated air is blown away from the cooler—ideally out of the case—and more room-temperature air is drawn in.

Today, there are 3 main approaches to cooling a CPU: air-cooling heatsinks, all-in-one liquid coolers, and full custom liquid cooling loops. The latter of these three is incredibly complex, and would easily require a separate guide. However, if you’re interested, this forum can be quite a good place to ask questions.

In days long past, removing a heatsink was a recipe for instant disaster, as modern thermal throttling mechanisms (designed to shut down PC components when they overheat above the generally accepted maximum of about 100 degrees Celsius) were not in place yet. However, just because Intel and AMD say CPUs can operate for at least their warranty period (usually between 1 and 3 years) at these temperatures, that doesn’t mean they should. Every system still needs a cooler.

First of all, the hotter an integrated circuit is, the more power it will consume (as can be proven with this formula), and its lifespan will decrease.

Puget Systems has an article where they analyze how much temperature affects Intel CPU performance (namely, core clocks and performance in floating-point compute). So, second of all, while 90 degrees Celsius is probably fine if your only goal is not sacrificing performance, 65-70 degrees Celsius is generally accepted as a good target.

Make sure the HSF is compatible with your motherboard, CPU socket, and case. For example, a HSF that is compatible with AMD's socket AM4 is not necessarily compatible with Intel's socket 1200. Multiple sockets sometimes use the same mounting system. For example: Intel sockets 1150, 1151, 1155, and 1156 all use the same HSF mounting system, so they share compatibility.

Make sure the HSF you buy will fit your case, and will not disturb the other components in your PC (your RAM, specifically).

To understand heatsink design, you also need to understand how air cooler designs have evolved as generations reach their theoretical performance limit. It started with simple, aluminum heatsinks for CPUs that required between 5 and 70 watts. These transported heat to relatively small fins. This technique worked well for a long time, and so a lot of people naturally thought that bigger fins would just mean better performance.

Not so. As temperature is conducted along a fin, the temperature of said fin will drop. As the fin gets closer to your ambient temperature, you will get no additional heat transfer from it.

As CPU TDPs stretched into the 75 - 150 watt range, thermal engineers turned to heatpipes. Heatpipes don’t inherently provide better cooling, but they do conduct heat much better than traditional metal, through both conduction and convection.

The thermal conductivity of copper is about 388 W/mK, while a heatpipe can have a conductivity of up to 10,000 to 100,000 W/mK. That is how massive heatsinks, like the Noctua NH-D15, can actually be effective.

Liquid coolers are still generally a step above air coolers, although this is changing quite quickly. Unlike heatsinks, AIOs have a clear ranking system, based on the size of their radiator, which consists of some number of fans that each have a diameter of either 120 or 140 millimeters. There are single-fan AIOs with one 120mm or one 140mm fan; dual-fan AIOs with a total of either 240 or 280 millimeters in fan real estate; and triple-fan AIOs. For three-fan models, 360-millimeter options are commonplace (i.e. three 120mm fans). Some companies have already made 420mm models (i.e. three 140mm fans), but these aren’t necessarily that commonplace yet.

Liquid cooling is generally considered to be better due to the high heat capacity of water and water-based coolants: simply speaking, heat capacity is how much heat can be absorbed by a substance before it changes temperature. Water and water-based coolants have a much higher heat capacity than most other substances. This is why pools and lakes can be exposed to the sun for hours on end, yet remain very cold to the touch.

This is because of a concept called hydrogen bonding. The oxygen atom in a water molecule is relatively electronegative, which means it attracts more electrons, which in turn gives it more of a negative charge than the adjacent hydrogen atoms. Consequently, this means that the hydrogen atoms of other water molecules will stick to the aforementioned oxygen atoms, and prevent them from moving around too much when heat is applied.

So, since heat is a product of thermal velocity, water can resist heat better than the metals commonly used in heatsinks. This means that if you have a waterblock attached to your CPU, you will be pumping heat into a substance that can actually hold it. The radiator attached to it then disperses the heat from this water outside of the case. This higher heat capacity may also lead liquid coolers to run quieter than comparably performing air coolers, whose fans may have to spin faster to dissipate heat at a greater rate.

Modern thermal paste is usually very good. Use whatever comes with your heatsink. Replacing the thermal paste on your stock heatsink may actually decrease cooling performance. If you want every last bit of cooling performance, do your research before buying thermal paste, because different pastes will perform differently based on your application method and the mounting pressure of your heatsink. You may also want to check out these thermal paste performance benchmarks.

The following is very rough, generalized information. Coolers that seem to fit into one tier can actually be a tier higher or lower if they’re well-designed or poorly designed, respectively. So, take this with a grain of salt.

Tier 1: 280/360/420mm liquid coolers, humongous air coolers

Most AIOs with a 280/360/420mm AIO fit into this tier. We’d go for an AIO from a well-known brand like Corsair, Cooler Master, or Deepcool, but if you have a personal or aesthetic preference, it’s probably not too critical to go for it.

Especially beefy air-cooled heatsinks also fit into this tier. This subject is quite controversial, so please do your own research if you’re looking for a top-of-the-line heatsink. Specifically, look for benchmarks featuring the CPU you’re planning to buy, and your workload (gaming, rendering, video editing, etc).

Deepcool’s Assassin III and Thermalright’s Silver Arrow IB-E Extreme are (subjective) examples of the latter. At the time of writing, Logical Increments uses this class of cooling for the Extremist and Monstrous tiers of our main chart.

Tier 2: 240mm liquid coolers, high-end air coolers

Most 240mm AIOs fit into this tier. Again, when in doubt, look for well-known brands.

The rest of the air-cooled heatsinks advertised as “high-end” fit into this tier. Some examples include Noctua’s NH-D15, be quiet!'s Dark Rock Pro 4, and Corsair's A500.

Tier 3: low-end 240mm liquid coolers, upper-midrange air coolers

This tier consists of 240mm AIOs that aren’t as well-performing as their Tier 2 counterparts (and cost less), and most midrange air-cooled heatsinks. This level of cooling is currently only used by the Enthusiast tier.

Tier 4: 120/140mm liquid coolers

AIOs with 120mm or 140mm radiators fit into this tier. Generally, however, buying these isn’t a very good decision outside of maybe aesthetics, as they cost more than the heatsinks from Tier 3 but perform a lot worse.

Not something we’d usually recommend buying, except in special circumstances (like certain small form factor builds, perhaps), as most people considering this tier would get better results from the less-expensive options in Tier 5 or the better-performing options in Tier 3.

Tier 5: Budget/midrange (tower-style) air coolers

A lot of fairly well-known budget heatsinks are in this tier: Cooler Master's Hyper 212 EVO V2, be quiet!’s Pure Rock 2, and Noctua's NH-U12S Redux.

Logical Increments uses coolers from this class across many tiers. While technically low on a tier list like this that surveys the whole market, this level of cooling is very popular for modern PCs as it generally has the best balance of price and performance. In fact, over on the main PC chart, all the builds from the Fair tier up to the Exceptional tier recommend coolers that would fit in this tier.

Tier 6: Low-profile air coolers, stock air coolers

Unfortunately for SFFPC lovers, low-profile heatsinks usually end up here, alongside most stock coolers included in the box with CPUs from AMD and Intel. This includes Noctua'’'s NH-L9i and CryoRig's CryoRig's C7.

When looking to build a system using a Threadripper or an Intel HEDT chip, you should consider using a special cooler designed for the socket in question. This is because the socket is physically much larger than a consumer socket like AM4 or LGA1200, and the coldplate of a traditional cooler that doesn't cover the entire IHS of this socket could negatively affect cooling performance.

Gamers Nexus shows a 10-degree temperature drop, and Anandtech claims a 20-degree temperature drop between a standard NH-U14s and one with a special coldplate.

It’s very difficult to find anything resembling a complete list of these coolers, so if you're looking for a competent cooling solution for one of these specialty platforms, please do your own research as to if the cooler you're considering has a version with a larger coldplate.

Check Frosty Tech and Silent PC Review for high-quality heatsink and fan reviews.

Ilya Rudnitskiy is a contributing writer for Logical Increments.

The Falcon is one of the founders of Logical Increments, and the original creator of its main build chart.

Logical Increments helps more than 2 million PC builders each year with hardware recommendations for any budget.