Pick the 360mm AIO unless your case is built for a 420mm radiator and your processor runs very hot under long loads. At matched noise levels, a good 360mm cooler gives up little to a 420mm model, and a 360 fits far more cases. Here, “360mm” means three 120mm fans on one radiator, and “420mm” means three 140mm fans. The difference that matters most is the physical size of the radiator, not the number on the box.
Our Top Picks
ARCTIC Liquid Freezer III Pro 360 A-RGBLiquid Freezer III Pro 360 A-RGB15.7 x 4.7 x 2.9 Inches4.5 PoundsCheck on Amazon
Top 3 picks at a glance
Quick Answer
- Fit first: a 360mm radiator is about 396 to 401 mm long and roughly 120 mm wide; NZXT’s 420mm Kraken Elite is 457 mm long and wider because it carries 140mm fans.
- Fan area: three 120mm fans cover 43,200 square millimeters and three 140mm fans cover 58,800, so the 420 has about 36 percent more nominal fan area (NZXT’s figures).
- Matched noise: Noctua’s published comparison found its 420mm and 360mm AIOs neck and neck at about 22 dB(A), with the 420 ahead by only 0.5 C even at a 300 W heat load. At full speed, the 420 was louder by up to about 5 dB(A).
- Choose the 420 only if your case lists 420mm support at the mounting spot you plan to use, and your chip runs near its limit in long all-core workloads.
What You Need
- Your case’s radiator support list. Look for the exact top, front, or side position, not just the headline “supports 420mm”.
- Three-fan spacing. A 420 radiator needs three 140mm fan positions in a row, spaced 140 mm apart on center.
- Clearance depth. Radiator thickness is typically 27 to 38 mm and fans add 25 to 30 mm, so budget about 52 to 68 mm of internal depth.
- CPU wattage under your real workload. Read it from a monitoring tool during a sustained all-core run, not from the box.
- Motherboard and memory clearance. Tall RAM heatsinks and VRM heatsinks can collide with a top-mounted radiator and fans.
- A tape measure. Measure the gap in the case, then compare with the radiator length including end tanks.
360mm vs 420mm by the Numbers
| Measure | 360mm AIO | 420mm AIO |
|---|---|---|
| Fans | Three 120mm | Three 140mm |
| Typical radiator length | About 396 to 401 mm | About 440 to 457 mm |
| Nominal fan area | 43,200 square mm | 58,800 square mm |
| Radiator thickness | 27 to 38 mm | 27 to 38 mm |
| Case support | Most mid-towers at the top or front | Mostly large towers, usually the front |
| Noise at full speed | Quieter than the 420 in Noctua’s data | Up to about 5 dB(A) louder in Noctua’s data |
| Noise-matched cooling | Close to equal | Close to equal |
Real length depends on the model: NZXT lists its Kraken Elite 360 radiator at 401 x 120 x 27 mm and Corsair lists its Nautilus 360 at 396 mm. Always compare the exact radiator, not the nominal size.
Will a 420mm Radiator Fit Your Case?
- Open the case maker’s specification page and find the radiator support table.
- Confirm it lists 420mm or 3x140mm for your intended position. Many cases that list 360 cannot take a 420, and few support 420 at the top.
- Check the maximum radiator thickness plus fan thickness. A 27 mm radiator with 25 mm fans needs about 52 mm; a 38 mm radiator with 30 mm fans needs about 68 mm.
- Measure the length available. A radiator with fans on is roughly 445 mm long and 165 mm wide.
- Check that RAM and VRM heatsinks clear the radiator if it is top-mounted.
- Make sure the pump sits below the highest point of the radiator, so air collects in the radiator rather than the pump. NZXT notes this positioning rule.
Worked example: your case lists a 360mm top mount with 55 mm of clearance. A Nautilus-style radiator with fans is 52 mm deep, so it fits. A 38 mm radiator with 25 mm fans needs 63 mm and does not. Cases that fit a 420 at the front often include the Fractal Design Torrent, Phanteks Enthoo Pro 2, Lian Li O11 Dynamic XL, and Corsair 7000D Airflow; confirm any case against its own specifications.
Cooling and Noise: What the Data Says
Marketing often claims the 420 runs several degrees cooler, because it has more surface area. Measured, noise-matched comparisons are less dramatic.
- Noctua’s own testing showed the 420mm model ahead at higher fan speeds, but it was noisier, up to about 5 dB(A). Normalized to about 22 dB(A), the two were neck and neck.
- Even at 300 W the 420 held only a 0.5 C lead in that noise-normalized run.
- EnosTech’s radiator testing found a thick 360 and a slim 420 nearly equal when noise was normalized, which shows that fin density and thickness matter as much as length.
- AnandTech measured the Arctic Liquid Freezer II 420 at 0.0783 C/W average thermal resistance, better than any cooler the reviewer had measured at that time, though it was on the loud side at maximum speed.
The practical conclusion: the specific cooler’s fans, block, and radiator design usually matter more than whether it is a 360 or 420.
Choosing by your situation
| Your situation | Better choice | Why |
|---|---|---|
| Mid-tower, top radiator mount | 360mm | Few mid-towers take a 420 at the top |
| Gaming with a modern 8 to 16 core chip | 360mm | Gaming loads rarely stress a good 360 |
| Long all-core rendering at the chip’s limit | 420mm if it fits | More headroom at the same low fan speed |
| Quiet build, fans kept below mid speed | Either; pick the better fans | Noise-matched results are near equal |
| Large tower with a front 420 mount | 420mm | Fits easily and airflow is good |
| Tight memory or VRM clearance | 360mm | Shorter and narrower |
As a rule of thumb, treat a 420 as a headroom purchase for sustained 200 to 300 W loads. This is judgment based on the noise-matched data above, not a manufacturer rating.
If It Does Not Work
- The radiator will not fit. Move it to another mount, choose a thinner radiator, or drop to 360mm. Do not force fans against RAM or the case panel.
- Temperatures are worse than expected. Check the pump header is set to full speed or a high fixed value, the fans are plugged into the correct PWM headers, and the cooler’s cold plate has the protective film removed.
- Gurgling or air noise. Reposition so the pump is not the highest point, then tilt the case gently to release air. Persistent noise after a day or two deserves a support ticket.
- Fans too loud. Lower fan speed at moderate loads using a curve rather than a flat setting.
- Cooler will not mount. Confirm the socket bracket for your CPU is installed. Some brands ship the AM5 bracket pre-installed.
Gear That Helps
Corsair Nautilus 360 RS ARGB – budget-friendly 360mm baseline
As an Amazon Associate we earn from qualifying purchases at no extra cost to you.
Corsair lists a 396 mm aluminum radiator, three RS120 ARGB fans at up to 2,100 RPM with 13.3 to 72.8 CFM, and 10 to 36 dBA. Support covers LGA1851, LGA1700, AM5, and AM4, with a five-year warranty. The fans daisy-chain to one motherboard header. Its caveat is that Corsair publishes no TDP rating, so treat it as a mainstream cooler rather than a headroom pick for the hottest chips.
Corsair iCUE LINK Titan II 360 RX – when you want fewer cables
Corsair lists RX360 II unified-frame fans at 400 to 2,100 RPM, 14.1 to 64.7 CFM, 10 to 32.8 dBA, and a FlowDrive 2 pump with a convex copper cold plate, backed by six years. It uses the iCUE LINK single-cable system. Corsair’s page names AM5, AM4, LGA1851, and LGA1700; the retailer title also mentions LGA1954, so confirm that socket on the listing. Confirm on the listing whether an iCUE LINK hub is included, since Corsair sells that hub separately for other iCUE LINK coolers.
ARCTIC Liquid Freezer III Pro 360 A-RGB – value-focused thermal option
Arctic’s Liquid Freezer III line is known for a thick radiator and a bundled Intel contact frame; Arctic says the stock Intel bracket puts over 40 kg of force on two points. A thicker radiator needs more case depth, so apply the clearance checklist above. Confirm radiator thickness, fan model, and socket support for this Pro version on the listing.
NZXT Kraken Elite 360 RGB – display-first 360mm
NZXT lists a 401 x 120 x 27 mm radiator, F360 RGB Core fans at 500 to 2,400 RPM, a Turbine pump at 1,200 to 2,800 RPM, and a six-year warranty. The LCD is the draw, though the listing says 2.36 inches while NZXT’s product page describes a 2.7-inch panel, so confirm which revision you are buying. The fans come in a single frame, which cleans up cabling but limits fan swaps.
Common Mistakes
- Trusting “supports 360mm” for a 420. The radiator is wider and longer, and the case needs 140mm fan spacing.
- Ignoring thickness. Radiator plus fans can exceed the panel clearance even when length fits.
- Comparing at different fan speeds. Judge cooling at matched noise, not at maximum RPM.
- Letting the pump be the highest point. Trapped air shortens pump life and raises noise.
- Buying on specs alone. The cooler’s fans and cold plate matter as much as radiator length.
- Skipping the RAM check. A top-mounted radiator can block tall memory modules.
Questions
Is a 420mm AIO worth the extra cost?
Usually not for gaming. Noise-matched data shows a gap of about 0.5 C in Noctua’s 300 W run. The 420 earns its place in a big case with long all-core loads, where extra radiator area gives headroom at lower fan speeds.
Will a 420mm AIO fit in my mid-tower?
Probably not at the top. Standard mid-towers usually top out at 360mm, and the radiator needs three 140mm positions plus clearance depth. Check your case’s support table for the exact position.
Are 140mm fans quieter than 120mm fans?
At the same airflow, larger fans can spin slower, which helps noise. NZXT notes that larger fans can move the same air at lower speeds, though real results depend on the fan design.
Does a bigger radiator cool the GPU too?
No. A CPU AIO only cools the processor. A big radiator may warm case air a little, so keep exhaust paths clear.
Which is easier to install, 360 or 420?
The 360. It is shorter, lighter, and compatible with far more cases and mounting positions.
Update History
- October 20, 2026 – Updated with specification checks and a revised product comparison.
- Check the product page for current specifications and availability before buying.
Sources
- Noctua – AIO radiator size FAQ (420, 360, and 240mm)
- NZXT – 240 vs 280 vs 360 vs 420 AIO guide and Kraken Elite 360 RGB specifications
- Corsair – Nautilus 360 RS ARGB and iCUE LINK Titan II 360 RX product specifications, and AIO sizing guide
- EnosTech – radiator cooling performance comparison
- AnandTech – Arctic Liquid Freezer II 420 review
- Overclock.net – community discussion of noise-normalized 360 vs 420 results
- Tom’s Hardware – Arctic Liquid Freezer III contact frame coverage
420mm and 360mm coolers worth considering
The four coolers at the top of this page are all 360mm models. If you decided that your case can take 420mm, or you want a different 360mm angle, these are the extra options to compare against them.
Noctua NL-LC1-42: The quiet 420mm option
The Noctua NL-LC1-42 is a 420mm all-in-one cooler with a 30mm slim radiator, according to its listing, and it is marketed around very quiet cooling and low pump noise. It sits in the premium price tier, and its appeal is exactly the acoustic point made earlier on this page: three large 140mm fans can move the same air at lower speed than three 120mm fans.
It is the cooler to look at if you already know you want a 420, own a case with explicit 420mm support, and care more about noise than about a flashy appearance. Compared with the Arctic Liquid Freezer III Pro 360 in the main list, it costs far more and gives you a bigger radiator, but a 360mm unit with good fans can come close on temperatures at a much lower price tier.
The slim 30mm radiator helps with clearance but reduces the amount of metal and liquid compared with thick radiators, so do not assume a bigger number on the box means a bigger gain. As with every 420, check that the radiator length, thickness and fan depth fit your case, and that tall memory does not collide with the top mount. Skip it if your case tops out at 360mm, or if you want built-in lighting or a screen.
NZXT Kraken Elite 420: The 420mm with a screen
The NZXT Kraken Elite 420 RGB is the larger sibling of the Kraken Elite 360 in the main list. It has a 2.36-inch LCD on the pump head and the F420 RGB Core single-frame fan unit, which holds three 140mm fans on one frame. It is a premium-tier cooler aimed at visible builds with a glass side panel.
The single-frame fan unit is a practical benefit: it mounts as one piece, which makes installation tidier in a case that supports it. The pump-head screen can show temperatures or custom images, which some buyers value. Compared with the Elite 360, you gain radiator area and the possible noise advantage, but you pay for it and lose compatibility with many mid-tower cases.
The drawbacks are price and fit. A 420 with a screen is a luxury tier product, and you should not choose it for cooling alone. Check the case specification for 420mm radiator support and for the fan frame dimensions, and confirm your motherboard has the headers and USB connection the software needs. Skip it if your CPU is mid-range, if your case only supports 360mm, or if you do not want to install vendor software.
Thermaltake TH420 V2 Ultra ARGB: A lower-priced 420
The Thermaltake TH420 V2 Ultra ARGB is a 420mm AIO with three 140mm PWM fans running between 500 and 1800 rpm, plus a 2.1-inch LCD on the water block, according to its listing. It sits in a mid-range tier for 420mm coolers, noticeably below the Noctua and NZXT models.
It answers the common question of whether a 420 has to be expensive. The answer is no: several 420mm units are priced in the same range as premium 360mm coolers. The fan speed range of 500 to 1800 rpm gives you room to run quiet at idle and ramp when the CPU is loaded.
The trade-offs are polish and acoustic refinement. Budget-tier 420 fans and pumps usually do not match Noctua-level noise tuning, and the included software and lighting vary by model. Check the radiator thickness against your case clearance. Skip it if you want the quietest pump and fans, or if your case cannot hold a 420.
be quiet! Pure Loop 3 360mm: The value 360
The be quiet! Pure Loop 3 360mm is a non-RGB all-in-one for builders who only need to keep a CPU cool with light overclocking. It uses three quiet 120mm fans, according to its listing, and sits in the budget tier for a 360mm unit.
It is the sensible pick if your decision after reading this page is to stay with a 360 and put the saved money into a better graphics card. It fits nearly any case that supports a 360mm radiator, and a plain design suits builds without a glass panel or without lighting.
The compromise is that it does not have the extra features of the Titan II or Kraken Elite, such as a screen or RGB lighting. It is also a conventional design, not the highest-performing 360mm cooler. Skip it if you need to cool a high-wattage CPU at the lowest noise, or if you want lighting synchronised with the rest of the build.
How much cooler is a 420mm than a 360mm?
Typical forum and review comparisons put the gap at a few degrees under sustained heavy loads, with some users reporting differences as small as one or two percent once noise is matched. The gain depends heavily on the specific cooler design, fan quality and CPU, so a well-designed 360 can match or beat a mediocre 420.
Is a 280mm AIO a good middle choice?
Often yes. Two 140mm fans can give cooling close to a 360mm on mainstream CPUs while running quieter, and a 280mm radiator fits in more cases than a 420.
Does a bigger radiator mean a quieter system?
It can. A larger radiator lets the fans run slower for the same cooling, which usually reduces noise, but pump noise and fan quality still matter.
Where should the pump sit?
Mount the radiator so the pump is not the highest point of the loop, because air collects at the top and can reach the pump. A front mount with the tubes at the bottom or a top mount with the tubes on the side are common choices.
Do I need a 420mm AIO for a Core i9 or Ryzen 9?
Not necessarily. A good 360mm AIO handles most high-end desktop CPUs. A 420 helps mainly under long sustained loads, in warm rooms or when you want the quietest fan profile.
Case fit checklist before buying a 420mm radiator
- Official support. Find the case specification page and look for explicit 420mm or 3x140mm radiator support at the exact mounting position: front, top or side. Support in one position does not guarantee the others.
- Radiator length. Nominal size is not the physical length. A 420 radiator is often around 450mm or more, so compare real dimensions.
- Thickness and fans. Add the radiator thickness to the fan thickness, since slim radiators are about 27 to 30mm and thicker designs go beyond that, and compare the total with available space.
- Memory and motherboard clearance. A top-mounted radiator can collide with tall RAM or VRM heatsinks, so check the clearance between the motherboard edge and the radiator.
- Tube length and orientation. Make sure the hoses reach the CPU block without kinking, and that the pump is not the highest point in the loop.
- Front-mount airflow. A front radiator pulls cool room air but delivers warm air to the GPU, so check overall airflow.
360mm or 420mm: a quick decision table
| Your situation | Better choice | Why |
|---|---|---|
| Mid-tower case with 360mm support only | 360mm | 420mm will not fit |
| Full-tower case with 420mm support, hot high-core CPU | 420mm | Lower noise at the same temperature |
| Mainstream 6 or 8 core CPU | 360mm or smaller | Extra area is rarely needed |
| Price-sensitive build | 360mm | More models and lower cost |
| Quiet-first build with a hot CPU | 420mm with quality fans | Bigger fans at lower speed |
Who should skip a 420mm AIO
If your CPU draws about 150 watts or less, the extra radiator area adds cost and usually little measurable gain. If your case lists support for only up to 360mm, there is no safe way to fit a 420. Builders who prefer a simpler installation should also avoid the additional measurements that a 420 demands.
