Cheapest 16GB server RAM ranked by price per GB

16GB server RAM: the workhorse module for home labs and small servers

16GB is the module size that spans the most server generations: high-capacity DDR3 RDIMMs for older Xeons, the mainstream DDR4 RDIMM for a decade of rack servers, ECC UDIMMs for small towers and NAS builds, and the entry DDR5 RDIMM for current platforms. The 183 16GB server and workstation modules above are ranked by price per gigabyte, from £1.07/GB to £91.03/GB (median £9.07/GB); the cheapest right now is Lafeier 16GB PC3-8500R DDR3 1066Mhz CL7 240Pin ECC REG Memory RAM 1.5V… at £17.11.

Which platforms use 16GB modules

• DDR3 RDIMM (usually 2Rx4 PC3L-12800R or PC3-14900R): Xeon E5 v1 and v2 servers such as the Dell PowerEdge R620 and R720 and HP ProLiant Gen8. Sixteen of them in a two-socket box gives 256GB for very little money.
• DDR4 RDIMM (PC4-2133P to PC4-2933Y): Xeon E5 v3 and v4 (PowerEdge R630 and R730, ProLiant Gen9) and first and second generation Xeon Scalable (PowerEdge R640 and R740, ProLiant Gen10).
• DDR4 ECC UDIMM: the HP ProLiant MicroServer Gen10 Plus (two slots, 32GB maximum, so 2x16GB fills it), Xeon E-2100 and E-2200 machines, and Ryzen builds on boards with ECC support. A common choice for TrueNAS and ZFS boxes.
• DDR5: 16GB is the smallest DDR5 RDIMM, used in Xeon Scalable 4th generation onward and EPYC 9004 and later, and the 16GB DDR5 ECC UDIMM suits Xeon E-2400 and W680 boards and AM5 boards that support ECC.

Populate by channel, not by slot count

Servers are rarely upgraded with a "kit" in the desktop sense; you buy single modules and fill channels evenly. Xeon E5 has four memory channels per socket, so 16GB modules go in fours (eight for a two-socket machine). First and second generation Xeon Scalable have six channels, so sets of six or twelve; EPYC 7002 and 7003 have eight. Filling one DIMM per channel across every channel gives far more bandwidth than doubling up on a few, and in a two-socket server each CPU should carry the same amount. The server's manual or the maker's online configuration guide gives the exact slot order.

Gotchas

RDIMMs, LRDIMMs and UDIMMs do not mix, and an ECC UDIMM board will not take RDIMMs. Match the rank (1Rx4, 2Rx4, 2Rx8) and speed of the modules already fitted; the whole system runs at the slowest module's speed and the CPU's own limit, so a PC4-2666V stick in a Xeon E5 v4 server runs at 2400. On DDR5 platforms with eight or twelve channels per socket, 16GB per channel is the minimum and a large build is often cheaper per GB at 32GB. The compatibility check guide covers reading the board's supported list.

Reading the table

The ECC and Buffered columns tell an RDIMM from an ECC UDIMM, and the title usually carries the PC3 or PC4 code and rank. Used modules are the norm here, and memory with ECC reports its own faults, so a used stick that passes a test is a low-risk buy. Compare against the 8GB and 32GB server pages, see the ECC RAM page for workstation and NAS use, or the 16GB desktop page if you need ordinary memory. Hubs: server RAM and every 16GB kit.