AIO radiator sizes. — 120, 240, 280, 360 or 420?

What the radiator actually does

An AIO (all-in-one) liquid cooler is a closed loop. The pump sits on the CPU, pulls heat into coolant, then circulates that warm coolant through the radiator where the fans dump it into the air. The radiator is the cooler — the pump only moves heat around. Pump power matters for flow rate, but radiator surface area dictates how much heat the system can dissipate per unit time.

Three things determine radiator cooling capacity: surface area (more fins, more contact with passing air), airflow through the radiator (CFM of the fans at their operating RPM), and radiator thickness (a 38mm-thick radiator holds more coolant and exposes more internal surface than a 27mm-thick one). For most consumer AIOs, thickness sits at 27mm — the differences between sizes come down to fin area and fan size.

Size-by-size breakdown

120mm — skip it

A 120mm AIO has one fan and roughly the surface area of a mid-range air cooler's heatsink, with a pump that adds noise and a small reservoir of coolant that will eventually permeate out. For the R900-R1,300 a 120mm AIO costs, a Deepcool AK500 air cooler (R600) beats it on cooling, noise, reliability and price. The only reason to buy a 120mm AIO is to fit in a Mini-ITX SFF case where a tower air cooler physically won't go.

240mm — the rational entry point

240mm AIOs handle every 65W chip easily and cope with 105W Ryzen 7 and Core i7 reasonably under load. The R1,400-R2,200 SA price range covers Corsair iCUE H100i, NZXT Kraken 240, DeepCool LS520 SE and ARCTIC Liquid Freezer III 240. Fits any standard mid-tower with a front or top 240mm radiator mount.

280mm — the quiet alternative

280mm uses two larger 140mm fans instead of two 120s. Same fan count, more surface area, larger fans that move similar air at lower RPM. The result is meaningfully quieter operation at the same thermal load. The catch: not every case supports 280mm — the radiator is wider and many ATX mid-towers spec front mounts at 240/360 only. Always verify the case manual before ordering.

360mm — the sweet spot

360mm is where AIO design hits its best price-to-performance ratio. Fits the vast majority of standard ATX mid-towers, cools every consumer CPU through Ryzen 9 7950X3D and Core i9-14900K at noise-controllable fan speeds, and the price step from 240 to 360 is usually only R400-R600. If your case supports it and your CPU is 105W or higher, default to 360.

420mm — for sustained heavy loads

420mm AIOs deliver 15-20% more surface area than 360mm and are quieter at the same thermal output, but they require a full-tower case (or a very specific mid-tower that explicitly supports 420mm) and add R1,500-R2,500 to the cost. Worth it for long Blender renders, Cinema 4D rigs and sustained 100% multi-thread workloads on overclocked HEDT chips. Not worth it for gaming.

Matching radiator size to your CPU's TDP

CPU TDP (Thermal Design Power) is the heat the cooler has to deal with at sustained load. Modern AMD and Intel chips boost well past their nominal TDP — a "65W" Ryzen 7 9700X can pull 88W under heavy load; a "125W" Core i7-14700K hits 253W peak. Size your radiator to peak power draw, not the marketing TDP.

Case compatibility — measure twice, order once

The single biggest AIO mistake is buying a radiator your case won't fit. Cases publish their radiator support in the spec sheet — read it before you order.

Things to check on the case spec page:

• Front-mount support — usually listed as "up to 360mm" or "up to 280mm".
• Top-mount support — many cases support smaller radiators on top than front (typically 240/280 only on top, with 360 reserved for front).
• Radiator + fan total clearance — a 360mm radiator is roughly 27mm thick; add 25mm for fans = 52mm of clearance needed. The case must specify this in the radiator section.
• RAM clearance — when top-mounting, the radiator + fan stack can collide with tall DDR5 sticks. Verify the case lists "RAM-clear top radiator".
• GPU clearance — when front-mounting, the radiator + fans can interfere with long GPUs. Check the case's "max GPU length with front radiator" spec.

Top-mount vs front-mount — what changes

There are two reasonable places to put an AIO in a tower case: at the top exhausting air upward, or in the front pulling in fresh air. Both work; they have different thermal trade-offs.

Front-mount (intake): the radiator gets ambient room-temperature air. CPU temps run 2-4°C lower. The downside is the warm air leaving the radiator now flows through the case toward the GPU and motherboard VRMs — those run 3-6°C hotter as a result.

Top-mount (exhaust): the radiator gets air that's already been warmed by the GPU and other components. CPU temps run 2-4°C higher than front-mount. The upside is the warm radiator exhaust leaves the case immediately, keeping the GPU and VRMs in cooler air.

Default choice: front-mount intake for CPU-bound workloads (gaming with a modest GPU, productivity), top-mount exhaust for GPU-heavy workloads (rendering with a high-end GPU, AI inference). For a balanced gaming build with a 4070-class card, either works within 2°C of the other.

Push, pull, push-pull — what actually matters

Push = fans on the intake side of the radiator, pushing air through. This is how every AIO ships by default. Works perfectly.

Pull = fans on the exhaust side, drawing air through. Functionally identical to push in cooling. Sometimes physically necessary if your case has front-panel mesh or filter restrictions that require the radiator to sit closer to the chassis.

Push-pull = fans on both sides. Adds 1-2°C of cooling at high RPM. The catch: now you have double the fans running at the same RPM, which means roughly +3 dB of noise. Only worth it for record-chasing or extreme overclocking. For a normal gaming or productivity build, push-pull is wasted money.

The biggest single acoustic factor in an AIO is fan RPM curve, not push/pull orientation. A 360mm radiator running fans at 800 RPM at idle and 1300 RPM under load is almost silent. The same radiator with fans pegged at 1800 RPM under load is irritating regardless of orientation.

SA picks per tier

Key takeaways

1. 360mm is the default sweet spot — cools every consumer CPU, fits most mid-towers, quiet at sane fan RPM.
2. Skip 120mm AIOs. A R600 Deepcool AK500 air cooler beats every 120mm AIO ever made.
3. 280mm trades 1-3°C of cooling for meaningfully lower noise vs 360mm. Quiet builds, consider it.
4. Front-mount intake is 2-4°C cooler on the CPU; top-mount exhaust is 3-6°C cooler on the GPU.
5. Verify case compatibility from the manual, not the marketing bullets. Account for fan thickness.

Frequently asked questions