RAM Calculator: How Much Memory Your PC Needs
Too little memory makes a PC stutter, and too much is money you'll never get back. Tell it what's in your PC and how you use it, and you'll get the right amount, the kit to buy, and exactly which slots to fill.
Build your memory plan
- Plan for
- Your PC now
- Rated speed
Slots are counted from the CPU. Most boards print these names beside each slot, and your manual has the final word.
Compare two kits by true latency
A faster kit often has a higher CL number. True latency puts both on one scale: CL × 2000 ÷ speed, as Corsair explains. A lower number responds sooner.
Kit A responds 0.6 ns sooner. Kit B moves more data each second.
The best RAM setup for most desktops
Two matched sticks is the right answer for almost every desktop. Intel and AMD desktop chips have two memory channels, and a matched pair uses both at once.
| Sticks | Slots on a 4-slot board | What you get |
|---|---|---|
| 1 | A2 | Single channel, with half the bandwidth |
| 2 | A2 and B2 | Dual channel, the best choice for most PCs |
| 3 | Avoid | One channel holds more than the other |
| 4 | All four | Dual channel, but DDR5 runs slower |
The slot order comes from ASUS's install guide: A2 is the second slot from the CPU and B2 is the fourth. Two sticks side by side in A1 and A2 share one channel, so they run in single channel.
Four DDR5 sticks cost you speed. AMD rates the Ryzen 9 9950X at DDR5-5600 with two sticks but only DDR5-3600 with four. For 64 GB, buy 2 × 32 GB rather than 4 × 16 GB.
How the calculator sizes your RAM
It starts from planning defaults, not tested requirements. That's 8 GB for office work, 16 GB for gaming or coding, 32 GB for streaming, video editing, or virtual machines, and 64 GB for 3D work.
Running more apps at once adds 25%, 50%, or 100%. The total rounds up to a two-stick kit size: 8, 16, 32, 64, or 128 GB for DDR4, and 16, 32, 48, 64, 96, or 128 GB for DDR5. If you already have enough, it says so.
Your real apps beat any preset. Adobe's Premiere requirements, for example, ask for 16 GB for HD video and at least 32 GB for 4K on Windows. Put a number like that in Fine-tune and it replaces the estimate.
Check the kit before you buy
Match the board
Find your exact board on its maker's support site and open the qualified vendor list (QVL), which lists tested kits. Match DDR4 or DDR5, the capacity per stick, and the total the board supports.
Not sure what's in your PC? Our free PC Reporter names your motherboard and shows your RAM's speed, slots used, and channel mode.
Buy one kit instead of adding to old sticks
Sticks sold together in one kit are tested as a set. Intel warns that mixed sticks may run below their rated speed or stop the PC from booting. Kingston says the same about adding a second kit, even one with the same part number.
Pick a speed your CPU supports
The calculator shows the speed your CPU maker rates the platform for. Kits faster than that rely on XMP or EXPO profiles, which are a memory overclock, so they aren't guaranteed to run at the speed on the box. You turn them on in your BIOS.
Workstations follow different rules
Threadripper boards have more channels and need one stick in each. AMD's platform page lists four channels for TRX50 and eight for WRX90, so the manual decides how many sticks to buy.
Plan the rest of the upgrade
- Compare next steps with the PC Upgrade Path Planner.
- Explore CPU and GPU pairing with the bottleneck checker.
- Estimate power needs with the power supply sizing tool.
- Look up game needs with the game compatibility checker.
- New stick not showing up? Try cleaning the RAM contacts.
- See where the slots sit in our motherboard parts guide.
