12 240 mm AIO liquid coolers, ranked by sustained cooling headroom. The Cooler Master Atmos II Stealth 240 ranks first: rated 280 W sustained, it keeps 120 of the 120 processors it can mount in the Excellent band and has 27 W of headroom on the Core i7-13700K (253 W).
How the ranking works: each cooler’s sustained dissipation rating (what it can remove continuously at acceptable noise, not a marketing peak) is set against every CPU’s boost power limit, Intel’s PL2 or AMD’s PPT. Headroom is the difference in watts; 25 W or more is Excellent. Coolers rank by how much of the CPU list they keep Excellent, then by value. The formula and data sources are on the methodology page.
27 W of headroom on the Core i7-13700K (253 W), the hungriest chip on this list. Liquid, so no RAM height limit, $89.50 on Amazon; needs a radiator mount in the case.
7 W of headroom on the Core i7-13700K (253 W), the hungriest chip on this list. Excellent on 99 of 120, up to the Ryzen 9 7900X. Liquid, so no RAM height limit, $46.90 on Amazon; needs a radiator mount in the case.
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply to the purchase of this product.
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All 12 ranked
Best 240mm AIO coolers ranked by sustained headroom
A sealed closed-loop liquid cooler with a pump block and a 120–420 mm radiator. Radiator length determines case compatibility; thickness plus fans determines top-mount clearance above the VRM heatsinks.
The continuous heat load, in watts, a cooler can remove at acceptable noise. This site uses realistic sustained figures rather than marketing peak numbers, and models temperature as ambient plus load ÷ rating × a per-load scale.
The cooler's sustained dissipation rating minus the CPU's boost power limit, in watts. Positive headroom lets fans run slower and quieter; 25 W or more is rated Excellent here.
The maximum junction temperature the maker allows, typically 95–100 °C. AMD lists 90 °C for the Ryzen 7 5800X3D, 89 °C for the 7800X3D and 95 °C for the 9800X3D. At TjMax the CPU throttles clocks to stay in place; it will not overheat, but it will lose performance.