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240 vs 280 vs 360 vs 420 mm AIO: which radiator size should you get?
For most gaming builds, a 280 mm or 360 mm AIO is the right choice: enough radiator area to cool high-end CPUs quietly, and it fits most mid-towers. Pick 240 mm for compact cases or mainstream CPUs, and 420 mm for the hottest CPUs, if your case lists 420 mm support in the spot you plan to use.
The number in an AIO's name tells you the fan setup the radiator is built for. Bigger radiators have more surface area to shed heat, but they need a case with room for them. Here's how to choose.
What do 240, 280, 360 and 420 mean on an AIO?
The size is the combined width of the fans the radiator holds: two 120 mm fans make a 240 mm radiator, two 140 mm fans make 280 mm, three 120 mm fans make 360 mm, and three 140 mm fans make 420 mm.
| Radiator | Fans | Nominal fan area | Typical fit |
|---|---|---|---|
| 240 mm | 2 x 120 mm | 28,800 mm² | Small form factor, Micro-ATX and most mid-towers |
| 280 mm | 2 x 140 mm | 39,200 mm² | Most mid-towers; some Micro-ATX and Mini-ITX cases |
| 360 mm | 3 x 120 mm | 43,200 mm² | Most mid-towers |
| 420 mm | 3 x 140 mm | 58,800 mm² | Larger mid-towers and full towers that list 420 mm support |
Nominal fan area is fan width multiplied by radiator length (for example, 120 mm x 240 mm). It's a quick way to compare how much surface the fans push air through. A 280 mm radiator has nearly as much area as a 360 mm radiator while using one fewer fan.
Which AIO size should I get?
Match the radiator to how much heat your CPU produces under sustained load, then confirm it fits. Your CPU's rated power, listed by Intel or AMD, is the best starting point: the higher it is, the more radiator area helps.
- 240 mm: a good fit for mainstream CPUs and compact builds. Simple to mount, fits almost anywhere.
- 280 mm: a strong all-rounder. Larger 140 mm fans can move the same air at lower speeds, which helps keep noise down.
- 360 mm: the common choice for high-end gaming and creator CPUs, with wide case support.
- 420 mm: the most area for the hottest CPUs and long sustained loads, if your case has room.
More radiator area gives you headroom: the cooler can handle the same heat with fans spinning slower, or more heat at the same fan speed. Going bigger than your CPU needs won't hurt, as long as it fits.
Will the radiator fit in my case?
Check three things: the case supports that radiator size at your chosen mount location, the radiator's real length fits, and the combined radiator + fan thickness clears your memory and motherboard.
- Size by location. Cases often list different limits for the top, front and side. "Supports 420 mm" may apply to only one location.
- Real length. A radiator is longer than its nominal size because of end tanks. The Kraken Core 240 RGB radiator measures 277 mm long, the Kraken Plus 360 RGB measures 401 mm, and the Kraken Elite 420 RGB measures 457 mm.
- Thickness. Add the radiator and fan thickness together. A 27 mm radiator with 26 mm fans needs 53 mm of space. Compare that with the case's "radiator + fan thickness" spec, especially for top mounting above tall memory.
- Tubing reach. Make sure the tubes reach the CPU block from your mount location without strain.
Where should I mount the radiator?
Top-mounted as exhaust and front- or side-mounted as intake are both valid. Top exhaust sends CPU heat straight out of the case. Front or side intake gives the radiator the coolest air but warms the air reaching your GPU slightly.
Whichever you choose, keep the pump below the highest point of the radiator so any air in the loop collects in the radiator, not the pump. Mounting the radiator on top or in front with the tubes at the bottom accomplishes this.
Should I get an AIO or an air cooler?
Both cool CPUs well. An AIO moves heat to a radiator where it can be exhausted directly and keeps the area around the socket clear. An air cooler has no pump and nothing to mount but the cooler itself.
- AIO strengths: handles high, sustained CPU loads, frees space around the memory and socket, and suits cases with limited cooler height.
- Air cooler strengths: simpler install, no pump, no radiator fit checks. Confirm the cooler's height against your case's CPU cooler clearance.
Which NZXT AIOs come in these sizes?
NZXT Kraken coolers come in 240, 280, 360 and 420 mm sizes. Three examples from their listed specs:
- Kraken Core 240 RGB has a 277 x 120 x 27 mm radiator, an F240 RGB Core fan (two fans in a single frame), and support for LGA 1851, 1700, 1200/115X, AM5 and AM4. View product
- Kraken Plus 360 RGB pairs a 401 x 120 x 27 mm radiator with the NZXT Turbine pump, a split-flow copper cold plate, and a 1.54 in (39.1 mm) display. View product
- Kraken Elite 420 RGB uses a 457 x 140 x 27 mm radiator, an F420 RGB Core fan (three 140 mm fans in one frame), and a 640 x 640 px IPS display. View product
See every size in CPU coolers.
Quick checklist
- Look up your CPU's rated power to gauge how much radiator area you need.
- Choose a mount location, then confirm the case supports that radiator size there.
- Compare the radiator's real length, not its nominal size, with the available space.
- Add radiator and fan thickness and check it against the case and your memory height.
- Confirm socket compatibility (for example, AM5 or LGA 1851).
- Plan for the pump to sit below the top of the radiator.
FAQ
Is a 360 mm AIO better than a 280 mm AIO?
A 360 mm radiator has slightly more nominal fan area (43,200 mm² vs 39,200 mm²), so it has a bit more cooling headroom. In practice, they're close. Pick whichever your case supports best.
Is a 240 mm AIO enough for gaming?
For many mainstream CPUs, yes. If your CPU has a high rated power and runs long, heavy workloads, a 280 mm or larger radiator gives you more headroom and quieter fan speeds.
Is a 420 mm AIO overkill?
Not if your case supports it. The extra area lets the fans run slower for the same heat load. If your case doesn't list 420 mm support at the location you want, a 360 mm or 280 mm cooler is the better choice.
Should the AIO radiator be intake or exhaust?
Either works. Top exhaust removes CPU heat directly. Front or side intake feeds the radiator cooler air. Just keep the case's overall intake and exhaust balanced.
Do I need to check RAM height for a top-mounted radiator?
Yes. A top radiator plus fans can overhang the memory slots. Check the case's top radiator + fan thickness spec against your memory height.
