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How to Test RAM on Windows

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This guide covers testing RAM using Windows' built-in mdsched tool and the popular third-party MemTest86, and how to interpret what each one reports.

Updated August 9, 2026 · PC Utility Hub Editorial Team

Option 1: Windows Memory Diagnostic (built-in)

  1. 1Press Windows key, type mdsched, and press Enter.
  2. 2Choose Restart now and check for problems.
  3. 3During the blue diagnostic screen, optionally press F1 to select Extended mode and increase Pass Count for a more thorough check.
  4. 4Let the PC reboot into Windows and check the result popup, or look it up in Event Viewer under System logs, source MemoryDiagnostics-Results.

mdsched is built into Windows and requires no download — it's the fastest first check.

Option 2: MemTest86 (third-party)

MemTest86 is a well-known independent, third-party tool (not part of Windows or Sysinternals) that boots outside of any OS and runs a more extensive battery of memory test algorithms than the built-in tool.

  1. 1Download MemTest86 from its official site onto a working computer.
  2. 2Create a bootable USB drive using the tool's included USB imaging utility.
  3. 3Boot the target PC from that USB drive (you may need to change the boot order or use a one-time boot menu key).
  4. 4Let it run at least one full pass of all test algorithms; multiple passes (or leaving it overnight) catch more intermittent errors.
  5. 5Review the on-screen pass/fail summary for each test and memory module.

Since MemTest86 boots independently of Windows, it can test RAM even when Windows won't start reliably.

Interpreting results

  • Zero errors after a full pass or two is a good sign but not an absolute guarantee, especially for intermittent faults.
  • Any reported error typically points to a specific RAM stick or slot — try testing sticks individually and in different slots to isolate the faulty one.
  • Persistent errors despite reseating/reordering RAM usually mean the module (or occasionally the motherboard slot) needs replacing.

Other steps if RAM tests clean but problems persist

  • Reseat RAM modules and check they're fully seated in their slots.
  • Update motherboard BIOS/UEFI firmware, since memory compatibility issues are sometimes firmware-related.
  • Run System File Checker to rule out corrupted system files causing similar symptoms to RAM faults.

Frequently asked questions

Is MemTest86 made by Microsoft?
No, MemTest86 is an independent third-party tool, unrelated to Microsoft or Sysinternals.
Which is more thorough, mdsched or MemTest86?
MemTest86 generally runs a broader set of test algorithms and boots independently of Windows, making it more thorough for stubborn or intermittent faults.
How many passes should I run?
At least one full pass as a baseline; for intermittent issues, running overnight for several passes catches more errors.

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