Quick answer: You allocate more RAM to Minecraft by editing the JVM argument -Xmx — in the launcher for your client, or in the startup command for a server. For example, -Xmx6G gives Minecraft up to 6 GB. Here’s how to do it for both, and how much you actually need.
Not enough RAM causes stutters, long chunk loading, and “Out of Memory” crashes — especially with modpacks. But over-allocating can hurt too. This guide covers the right way to set memory for the client and for a server, plus how to size it. Need a number fast? Use our free Minecraft RAM Calculator.
How to Allocate RAM to the Minecraft Client
In the official launcher:
- Open the Minecraft Launcher and go to the Installations tab.
- Hover over your installation, click the three dots, and choose Edit.
- Click More Options to reveal the JVM Arguments field.
- Find the value
-Xmx2G(the default is usually 2 GB). Change the number — for example-Xmx6Gfor 6 GB. Only change this first number; leave the rest of the arguments alone. - Click Save and launch. Modpacks from CurseForge/Modrinth launchers have a simple RAM slider in their settings instead.
How to Allocate RAM to a Minecraft Server
A server’s memory is set in its startup command with two flags: -Xmx (maximum RAM) and -Xms (starting RAM). A typical line looks like:
java -Xmx4G -Xms4G -jar server.jar noguiSetting -Xmx and -Xms to the same value (here 4 GB) is common for servers, so the JVM reserves it all up front. If you host with a provider, you usually don’t touch the command at all — your Minecraft server hosting plan’s RAM is set by the plan you pick, and the panel handles the flags for you.
How Much RAM Do You Need?
- Vanilla / a few friends: 2–4 GB is plenty.
- Paper/Spigot with plugins: 4–6 GB for a small-to-medium community.
- Modpacks: 6–10 GB+ — heavy kitchen-sink packs are the hungriest thing you can run.
- Big communities / many chunks loaded: scale up with player count and view distance.
Don’t Over-Allocate
More RAM is not automatically better. Two rules:
- Never allocate all your system RAM. Leave 1–2 GB for your operating system, or you’ll cause worse stutters than you fix.
- Giving a server far more than it needs can lead to longer garbage-collection pauses (lag spikes). Match the RAM to the workload rather than maxing it out — the RAM Calculator helps you pick.
If you’re still lagging after adding RAM, the fix is often server settings, not memory — see our guide to reducing Minecraft server lag.
FAQ
What does -Xmx mean?
-Xmx is the JVM’s maximum heap size — the most RAM Minecraft is allowed to use. -Xms is the starting heap size. -Xmx6G means “up to 6 GB.”
Is more RAM always better for Minecraft?
No. Allocate what the workload needs and leave headroom for your OS. Over-allocating can cause longer garbage-collection lag spikes.
How much RAM for a modded server?
Most modpacks want 6–10 GB or more, depending on the pack size and player count. Lighter Fabric performance packs need less than heavy Forge kitchen-sink packs.
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