You do not get to choose between DDR4 and DDR5 unless you are also choosing a motherboard: the two are keyed differently and fit only their own boards. Where you do have the choice, the honest answer in 2026 is that DDR4 costs less per gigabyte (£6.70/GB median today against £16.71/GB for DDR5) and performs within a few percent in most software, while DDR5 is the platform of every new CPU and the only option for the fastest systems.
The physical key notch sits in a different place on each generation, so a mistake cannot be forced. The listing title on this site always states the generation, and the DDR4 and DDR5 pages are filtered to one each.
DDR5 starts where DDR4 ends: base speed 4800MT/s against DDR4's 2133 to 3200, with common kits at 5600 to 6400 and enthusiast kits above 8000. Each module has two independent 32-bit sub-channels instead of one 64-bit channel, which improves efficiency, and power management moved onto the module. Every DDR5 stick has on-die ECC that corrects errors inside the chip during refresh; that is a manufacturing necessity for the denser dies rather than the full ECC a server uses, and it does not protect data on its way to the CPU.
Capacity is the other real change. DDR5 introduced 24GB and 48GB modules, so 2x24GB (48GB) and 2x48GB (96GB) kits exist alongside the traditional sizes, and 64GB single modules arrived in 2026, which makes 128GB possible in two slots on supporting boards.
Less than the headline numbers. Latency in nanoseconds is similar: DDR4-3600 CL16 and DDR5-6000 CL30 both come out around 9 to 10ns, because the higher clock and the higher CL cancel out. Games that are limited by the graphics card, which is most of them at 1440p and above, show no difference at all. CPU-limited games and memory-bandwidth-heavy work (compression, some simulation, integrated graphics) show DDR5 ahead by 5 to 15 percent on the same CPU where a direct comparison is possible, which is really only on 12th to 14th-gen Intel.
The bigger performance jump comes from the CPU you pair it with, not the memory. A Ryzen 7 9800X3D on DDR5 is a much faster gaming CPU than a 5800X3D on DDR4, but that is the CPU and the platform, and the memory is along for the ride.
This is where the live data earns its keep, because the gap moves. On the kits we track right now the median DDR4 kit costs £6.70 per gigabyte and the median DDR5 kit £16.71/GB. A year ago those figures were £2.98/GB and £3.68/GB, so DDR4 has moved +125% over twelve months and DDR5 +354% (index of 952 kits with a full year of history, updated 11 September 2026). Both generations rose through 2026 as DRAM makers moved capacity to AI accelerators; the price guide has the detail.
Not for the memory. Moving to DDR5 means a new motherboard and a new CPU, so the question is really whether you want a new platform. If your DDR4 machine has 16GB, the cheapest useful upgrade is a second 2x8GB kit or a 2x16GB kit from the DDR4 page, and a 5800X3D or 5700X3D if it is AM4. If you are building new, buy DDR5 because every current platform requires it, and buy 32GB as 2x16GB at 6000 CL30 (AMD) or 6000 to 6400 (Intel) from the 32GB page.
Anything before roughly 2015 is DDR3: 240-pin desktop modules at 1333 or 1600MHz, and the DDR3L low-voltage variant that laptops after 2013 require. It is still worth upgrading an old machine from 4GB to 8GB or 16GB, and used DDR3 is very cheap per gigabyte (£3.52/GB median), but there is no path from a DDR3 board to anything newer without replacing the board.