beginner performance

How to Allocate More RAM to Minecraft

Learn how to allocate more RAM to Minecraft in every launcher: vanilla, CurseForge, MultiMC, and Prism. Includes how much RAM you actually need and common mistakes to avoid.

Minecraft’s default RAM allocation is often too low, especially when using mods, shaders, or large resource packs. Increasing the memory available to the game can eliminate stuttering, reduce lag spikes, and prevent out-of-memory crashes. This guide covers how to allocate more RAM in every popular launcher, how much you actually need, and common mistakes that can make performance worse.

How Much RAM Should You Allocate?

More RAM is not always better. Allocating too much RAM is one of the most common Minecraft performance mistakes. Here is what you actually need:

SetupRecommended RAM
Vanilla Minecraft (no mods)2-3 GB
OptiFine or Sodium only2-4 GB
Light modpack (20-50 mods)4-6 GB
Heavy modpack (100+ mods)6-8 GB
Shaders + HD resource pack4-6 GB
Shaders + heavy modpack + HD pack8-10 GB

Why Too Much RAM is Bad

When you allocate 16 GB or more to Minecraft, Java’s garbage collector has to clean up a massive memory space. This causes longer and more severe lag spikes (called “GC pauses”) because the garbage collector takes longer to scan and free unused memory. You end up with smooth gameplay interrupted by periodic freezes — sometimes lasting half a second or more.

The sweet spot for most players is 4-6 GB. Even heavily modded setups rarely benefit from more than 8-10 GB. If you are experiencing issues at 8 GB, the problem is almost certainly not RAM — it is something else (CPU bottleneck, slow storage, or a mod issue).

Leave RAM for Your System

Your operating system, browser, Discord, and other programs need RAM too. A general rule:

  • 8 GB total system RAM — allocate no more than 3-4 GB to Minecraft
  • 16 GB total — allocate 4-8 GB
  • 32 GB total — allocate 6-10 GB (there is rarely a reason to go higher)

Vanilla Minecraft Launcher

The official Minecraft Launcher lets you set RAM through JVM arguments in the installation settings.

Step-by-Step

  1. Open the Minecraft Launcher
  2. Click Installations at the top
  3. Hover over the installation you want to modify (e.g., “OptiFine 1.21” or “Latest Release”)
  4. Click the three dots icon on the right, then Edit
  5. Click More Options to expand additional settings
  6. Find the JVM Arguments field. It will contain something like: 
    -Xmx2G -XX:+UnlockExperimentalVMOptions -XX:+UseG1GC ...
  7. Change the -Xmx value to your desired RAM amount:
    • -Xmx4G for 4 GB
    • -Xmx6G for 6 GB
    • -Xmx8G for 8 GB
  8. Click Save

The -Xmx flag sets the maximum heap size. Java will use up to this amount but not necessarily all of it.

Optional: Set Minimum RAM

You can also add -Xms to set the minimum RAM allocation:

-Xms4G -Xmx6G

This tells Java to start with 4 GB and grow up to 6 GB. Setting -Xms equal to -Xmx (e.g., -Xms6G -Xmx6G) pre-allocates all the memory at startup, which can reduce GC pauses by preventing dynamic heap resizing. This is a good practice for modded setups.

CurseForge / Overwolf Launcher

CurseForge makes RAM allocation easy with a simple slider.

Step-by-Step

  1. Open the CurseForge app
  2. Click the gear icon (Settings) in the bottom left corner
  3. Select Minecraft from the left sidebar (under Game Specific)
  4. Find the Java Settings section
  5. Adjust the Allocated Memory slider to your desired amount (e.g., 6144 MB for 6 GB)
  6. Close settings — changes apply automatically to all modpacks

Per-Profile Override

If you want different RAM for different modpacks (e.g., 4 GB for vanilla, 8 GB for a heavy modpack):

  1. Right-click the modpack
  2. Select Profile Options
  3. Enable Use Custom Java Memory
  4. Set the Max Memory Allocation

MultiMC / MultiMC (Cracked)

MultiMC provides clean per-instance memory control.

Step-by-Step

  1. Open MultiMC
  2. Right-click the instance you want to configure
  3. Select Edit Instance
  4. Go to the Settings tab
  5. Check the Memory checkbox to enable custom memory settings
  6. Set Minimum memory allocation to your desired minimum (e.g., 2048 MB)
  7. Set Maximum memory allocation to your desired maximum (e.g., 6144 MB)
  8. Close the settings window

MultiMC uses megabytes instead of gigabytes:

GBMB
2 GB2048 MB
3 GB3072 MB
4 GB4096 MB
6 GB6144 MB
8 GB8192 MB
10 GB10240 MB

Prism Launcher

Prism Launcher (the community fork of MultiMC) uses a nearly identical interface.

Step-by-Step

  1. Open Prism Launcher
  2. Select the instance you want to configure
  3. Click Edit on the right sidebar (or right-click > Edit)
  4. Go to the Settings tab
  5. Check Memory to enable custom settings
  6. Set your Minimum memory allocation and Maximum memory allocation
  7. Close the window — settings save automatically

Global Default (All Instances)

To set a default for all instances:

  1. Go to Settings (top menu or gear icon)
  2. Click Java in the left sidebar
  3. Adjust the memory values under Memory
  4. These apply to any instance that does not have custom overrides

ATLauncher

Step-by-Step

  1. Open ATLauncher
  2. Click Settings at the top
  3. Go to the Java/Minecraft tab
  4. Find Maximum Memory/RAM
  5. Set to your desired amount (in MB)
  6. Click Save

GDLauncher

Step-by-Step

  1. Open GDLauncher
  2. Click the gear icon (bottom left)
  3. Go to Java
  4. Adjust the Memory slider
  5. Close — saves automatically

Tlauncher

Step-by-Step

  1. Open TLauncher
  2. Click the gear icon next to the Play button
  3. In the settings window, find the Allocated RAM or JVM Arguments field
  4. Adjust the -Xmx value in JVM arguments or use the memory slider
  5. Save

Advanced JVM Arguments

For players who want optimal garbage collection performance, these advanced arguments can help reduce lag spikes beyond what simple RAM allocation provides.

-Xms4G -Xmx4G -XX:+UnlockExperimentalVMOptions -XX:+UseG1GC -XX:G1NewSizePercent=20 -XX:G1ReservePercent=20 -XX:MaxGCPauseMillis=50 -XX:G1HeapRegionSize=32M

What each flag does:

  • -Xms4G -Xmx4G — allocate exactly 4 GB (prevents heap resizing)
  • -XX:+UseG1GC — use the G1 garbage collector (best for Minecraft)
  • -XX:G1NewSizePercent=20 — 20% of heap reserved for new objects
  • -XX:G1ReservePercent=20 — 20% reserved to prevent allocation failures
  • -XX:MaxGCPauseMillis=50 — target max GC pause of 50ms (smooth gameplay)
  • -XX:G1HeapRegionSize=32M — larger regions for fewer GC operations

Aikar’s flags are widely used for Minecraft servers but also work well for client-side:

-Xms4G -Xmx4G -XX:+UseG1GC -XX:+ParallelRefProcEnabled -XX:MaxGCPauseMillis=200 -XX:+UnlockExperimentalVMOptions -XX:+DisableExplicitGC -XX:+AlwaysPreTouch -XX:G1NewSizePercent=30 -XX:G1MaxNewSizePercent=40 -XX:G1HeapRegionSize=8M -XX:G1ReservePercent=20 -XX:G1HeapWastePercent=5 -XX:G1MixedGCCountTarget=4 -XX:InitiatingHeapOccupancyPercent=15 -XX:G1MixedGCLiveThresholdPercent=90 -XX:G1RSetUpdatingPauseTimePercent=5 -XX:SurvivorRatio=32 -XX:+PerfDisableSharedMem -XX:MaxTenuringThreshold=1

These flags optimize G1GC specifically for Minecraft’s memory allocation patterns. Replace 4G with your desired amount.

Common Mistakes

Mistake 1: Allocating Too Much RAM

The number one mistake. Allocating 16 GB or 32 GB to Minecraft does not make it faster. It makes garbage collection pauses longer and more disruptive. Stick to 4-8 GB for almost all setups. See the table at the top of this guide.

Mistake 2: Using 32-Bit Java

32-bit Java cannot address more than about 1.5 GB of memory regardless of your settings. If you set -Xmx4G but have 32-bit Java, the game will crash or fail to launch.

How to check:

  1. Open a terminal or command prompt
  2. Run java -version
  3. Look for “64-Bit” in the output. If it says “32-Bit” or does not specify, install 64-bit Java.

Modern Minecraft (1.17+) ships with its own 64-bit Java runtime, so this is mainly an issue if you are using a custom Java installation or an older third-party launcher.

Mistake 3: Editing the Wrong Profile

In the vanilla launcher, each installation profile has its own JVM arguments. Changing the arguments for “Latest Release” does not affect your “OptiFine 1.21” profile. Make sure you are editing the profile you actually play on.

Mistake 4: Not Having Enough System RAM

If your system has 8 GB total and you allocate 6 GB to Minecraft, your operating system is left with 2 GB. This will cause system-wide slowdowns, desktop freezes, and potentially force the OS to use disk swap (which is catastrophically slow). Always leave at least 2-4 GB for your system.

Mistake 5: Confusing RAM with VRAM

RAM (system memory) and VRAM (GPU memory) are different. Allocating more RAM to Minecraft does not give your GPU more VRAM. If your GPU is running out of VRAM (visible as texture corruption or crashes when loading large resource packs with shaders), you need to reduce shader quality, resource pack resolution, or render distance — not allocate more system RAM.

Mistake 6: Forgetting to Check After Launcher Updates

Some launchers reset JVM arguments after updates. After updating your launcher, verify that your RAM allocation settings are still what you set them to.

How to Check Your Current RAM Usage

In-Game (F3 Debug Screen)

Press F3 while in a world. Look at the top right of the screen for a line like:

Mem: 45% 1843/4096 MB

This tells you:

  • 45% — current memory usage as a percentage
  • 1843 MB — currently used memory
  • 4096 MB — total allocated memory (your -Xmx value)

If the percentage regularly hits 90-95% and you see stuttering, you may need to allocate more. If it stays below 50%, you have allocated more than you need and could reduce it.

Garbage Collection Monitoring

If you see the memory percentage climb to 80-90%, drop suddenly, then climb again in a sawtooth pattern — that is normal garbage collection. The “drop” moments are GC pauses. If those pauses are causing visible stutters:

  1. Try setting -Xms equal to -Xmx to prevent heap resizing
  2. Use the advanced JVM arguments listed above
  3. Reduce allocation if it is excessively high (lowering from 12 GB to 6 GB often reduces stutter)

Verifying Your Changes

After changing RAM allocation:

  1. Launch Minecraft with the modified profile
  2. Load into a world
  3. Press F3
  4. Verify the total memory shown matches your -Xmx value
  5. Play normally and observe whether stuttering and lag spikes have improved

If the memory shown is still the old value, your changes did not apply. Double-check that you edited the correct profile and that the launcher saved your changes.

When RAM Is Not the Problem

If you have allocated 4-6 GB and still experience poor performance, the issue is likely elsewhere:

  • Low FPS (constant) — CPU or GPU bottleneck. Install OptiFine or Sodium, and tune your video settings.
  • Periodic freezes every few minutes — GC pauses. You may have too much RAM allocated, not too little. Try reducing to 4 GB with the advanced JVM arguments above.
  • Lag spikes when loading new chunks — storage speed. Minecraft loads chunks from disk. An SSD dramatically improves chunk loading compared to an HDD.
  • Lag spikes in specific areas — entity or redstone overload. Too many mobs, item frames, or complex redstone in one area causes CPU spikes that RAM cannot fix.

Getting Minecraft running smoothly is a combination of adequate RAM, optimized settings, and appropriate mods for your hardware. If you have not already, check our OptiFine settings guide for the video settings that have the biggest impact on frame rates.