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How to Get the Number of Memory Slots in a Batch Script

When planning a memory upgrade for a computer, one of the first and most important questions is, "How many RAM slots does it have, and how many are free?" Knowing the number of physical memory slots on the motherboard is essential for determining a machine's maximum memory capacity and for purchasing the correct memory kits.

This guide will teach you how to get this hardware detail using the powerful, built-in WMIC (Windows Management Instrumentation) command. You will learn the correct query to find the total number of slots and how to combine that with another query to determine how many are currently in use, allowing your script to report on available upgrade paths.

danger

CRITICAL NOTE: Querying low-level hardware information is a privileged operation. For the most complete and accurate results, your script must be run with full administrator privileges.

The Core Command: WMIC MEMPHYSICAL​

The WMIC (Windows Management Instrumentation Command-line) utility is the standard tool for querying system hardware. The MEMPHYSICAL alias provides access to information about the physical memory layout of the system.

Command: WMIC MEMPHYSICAL GET MemoryDevices

  • MEMPHYSICAL: The WMI class for the physical memory array on the motherboard.
  • GET MemoryDevices: The MemoryDevices property of this class returns the total number of memory slots available on the motherboard (whether they are populated or not).

Basic Example: Getting the Total Number of Slots​

Running the basic WMIC command gives you a simple, direct answer.

@ECHO OFF
ECHO --- Querying Total Memory Slots ---
ECHO This may take a moment...
ECHO.

WMIC MEMPHYSICAL GET MemoryDevices

The command produces a header and the number of slots. This output tells us the motherboard has a total of 4 RAM slots.

MemoryDevices
4

Determining Used and Free Slots​

Knowing the total is good, but knowing how many are free is even better. To do this, we need to combine our first query with a second one that counts the number of installed memory chips. We can do this with the WMIC MEMORYCHIP command.

The Logic:

  1. Get the total number of slots from WMIC MEMPHYSICAL.
  2. Get a list of all installed RAM sticks from WMIC MEMORYCHIP.
  3. Count the number of sticks found.
  4. Calculate Free Slots = Total Slots - Used Slots.

Parsing the Output with FOR /F for Scripting​

To automate this logic, we need to capture the output of these commands into variables using FOR /F loops.

@ECHO OFF
SETLOCAL
SET "TotalSlots="
SET "UsedSlots=0"

ECHO --- Capturing Memory Slot Details ---
ECHO.

REM --- Step 1: Get the total number of physical slots ---
FOR /F "skip=1" %%S IN ('WMIC MEMPHYSICAL GET MemoryDevices') DO (
    SET "TotalSlots=%%S"
    GOTO :GotTotal
)
:GotTotal
FOR %%N IN ("%TotalSlots%") DO SET "TotalSlots=%%~N"

REM --- Step 2: Count the number of installed memory chips ---
FOR /F "skip=1" %%C IN ('WMIC MEMORYCHIP GET Capacity') DO (
    SET /A "UsedSlots+=1"
)

ECHO Total Memory Slots on Motherboard: %TotalSlots%
ECHO Slots Currently in Use:            %UsedSlots%

REM --- Step 3: Calculate the number of free slots ---
SET /A "FreeSlots = %TotalSlots% - %UsedSlots%"
ECHO Available (Free) Slots:            %FreeSlots%

ENDLOCAL
note

The second FOR %%N ... loop is a standard trick to clean invisible trailing characters from WMIC output.

Common Pitfalls and How to Solve Them​

  • Administrator Rights: For the most reliable and complete hardware information, you must run the script as an Administrator.

  • Information Accuracy: The data provided by WMIC is dependent on the accuracy of the information programmed into the system's firmware (BIOS/UEFI) by the manufacturer. On rare occasions with generic or unusual hardware, this information may be incorrect or missing.

  • WMIC Output Quirks: WMIC can sometimes produce extra blank lines or invisible trailing characters. The scripts above account for this by using GOTO to exit the first loop immediately and by "cleaning" the variable in a second loop.

Practical Example: A Full RAM Inventory Report Script​

This script combines the slot count with a detailed list of what is installed in each slot, providing a comprehensive RAM inventory.

@ECHO OFF
SETLOCAL ENABLEDELAYEDEXPANSION

ECHO --- Full System RAM Inventory Report ---
ECHO.

REM --- Get Total and Used Slots ---
SET "TotalSlots=" & SET "UsedSlots=0"
FOR /F "skip=1" %%S IN ('WMIC MEMPHYSICAL GET MemoryDevices') DO (SET "TotalSlots=%%S" & GOTO :GotTotal)
:GotTotal
FOR %%N IN ("%TotalSlots%") DO SET "TotalSlots=%%~N"

FOR /F "skip=1" %%C IN ('WMIC MEMORYCHIP GET Capacity') DO SET /A "UsedSlots+=1"
SET /A "FreeSlots = %TotalSlots% - %UsedSlots%"

ECHO --- Summary ---
ECHO Total Slots: %TotalSlots%
ECHO Used Slots:  %UsedSlots%
ECHO Free Slots:  %FreeSlots%
ECHO =======================================
ECHO.
ECHO --- Installed Module Details ---
ECHO.

REM --- List details for each installed chip ---
FOR /F "skip=1 delims=" %%L IN ('WMIC MEMORYCHIP GET Capacity^,DeviceLocator^,Manufacturer^,Speed /FORMAT:CSV') DO (
    FOR /F "tokens=2-5 delims=," %%A IN ("%%L") DO (
        SET "CapacityBytes=%%A"
        SET "Slot=%%B"
        SET "Mfg=%%C"
        SET "Speed=%%D"
        
        REM Clean the variables and convert bytes to GB
        FOR %%N IN ("!CapacityBytes!") DO SET "CapacityBytes=%%~N"
        FOR /F %%G IN ('powershell -Command "!CapacityBytes! / 1GB"') DO SET "CapacityGB=%%G"
        
        ECHO Slot: !Slot! -- !Mfg! -- !CapacityGB! GB -- !Speed! MHz
    )
)

ENDLOCAL

Conclusion​

The WMIC utility is the definitive, built-in tool for getting detailed hardware information, including the number of physical memory slots on a motherboard.

  • To get the total number of slots, use WMIC MEMPHYSICAL GET MemoryDevices.
  • To find the number of used slots, count the results from WMIC MEMORYCHIP.
  • You can then easily calculate the number of free slots.
  • Always run your script as an Administrator for the most accurate and complete results.

By combining these two WMIC queries, you can write powerful inventory scripts that provide a complete picture of a system's memory configuration and upgrade potential.

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