RAM & memory, ranked by value

RAM (random-access memory) is your computer’s short-term working memory — the fast, volatile space where the operating system, open applications and active files live while the machine is running. Unlike the storage on this site, it doesn’t keep data when the power goes off; its job is speed, feeding the CPU far faster than any drive can. Having enough RAM is what lets you keep many browser tabs, applications and virtual machines open without the system slowing to a crawl as it swaps data to disk. Too little RAM bottlenecks even the fastest NVMe build.

Memory comes in distinct, non-interchangeable forms. The generation — DDR4 or the newer, faster DDR5 — must match your motherboard, and the two are physically incompatible. The module shape depends on the machine: full-size UDIMMs for desktops, compact SODIMMs for laptops and mini-PCs, and registered RDIMMs (and LRDIMMs) for servers and workstations that need many large modules running stably. Within a generation, capacity per stick, speed (MT/s), latency timings and whether the modules support ECC error correction all shape both price and suitability. Because RAM capacity isn’t measured in terabytes, we rank these by price and capacity rather than $/TB — buy the right type for your platform first, then optimise on value.

UDIMM vs SODIMM vs RDIMM, and DDR4 vs DDR5

Two things must match before price matters: the memory generation your board accepts, and the physical module type your machine takes. Get either wrong and the RAM simply won’t work.

Check your motherboard or laptop manual for the supported generation, module type, maximum capacity per slot and whether ECC is required. DDR4 and DDR5 are keyed differently and will not fit the wrong slot. For builders pairing memory with fast storage, see our drive selection guide and NAS guide.