How much RAM does a Minecraft server actually need?

Short version: most servers need far less RAM than hosts sell you, and once you have enough, adding more does nothing for lag. RAM stops your server from crashing with an out-of-memory error; it does not raise your TPS. Low TPS is almost always a CPU, plugin, or chunk-loading problem.

Here's what actually works as a starting point.

Quick reference

| Server type | Players | Sensible starting RAM | |---|---|---| | Vanilla / Paper | 1–10 | 2–3 GB | | Vanilla / Paper | 10–30 | 4–6 GB | | Plugins (20–40) | 10–40 | 6–8 GB | | Light modpack (~80 mods) | 3–10 | 6–8 GB | | Heavy modpack (150+ mods, e.g. ATM) | 5–15 | 10–16 GB |

These are starting points, not ceilings. Watch your actual usage and adjust — which is the whole point of the next section.

Why more RAM won't fix your lag

If your server stutters, the instinct is to throw RAM at it. It rarely helps, because Minecraft's tick loop is single-thread CPU-bound. A 200-mod pack on 32 GB will still drop to 12 TPS if one mod is scanning every chunk each tick. Admins on r/admincraft say this constantly — the highest-voted version is blunt: "adding more isn't going to help your low TPS woes."

What does help:

• A high-clock CPU. Single-thread performance is what the tick loop needs.
• Profiling with Spark. Run /spark profiler and read the flame graph — it tells you exactly which mod or task is eating the tick.
• Sane view/simulation distance. Dropping simulation-distance from 10 to 6 often does more for TPS than doubling RAM.

Give the server only as much RAM as it needs to avoid garbage-collection thrash — then stop.

Aikar's flags (use them)

Default JVM settings garbage-collect badly under Minecraft's allocation pattern. Aikar's flags tune the G1 collector for short, predictable pauses. On a managed host these are usually pre-applied; if you run your own, start the server with them:

java -Xms8G -Xmx8G -XX:+UseG1GC -XX:+ParallelRefProcEnabled -XX:MaxGCPauseMillis=200 \
  -XX:+UnlockExperimentalVMOptions -XX:+DisableExplicitGC -XX:G1NewSizePercent=30 \
  -XX:G1MaxNewSizePercent=40 -XX:G1HeapRegionSize=8M -XX:G1ReservePercent=20 \
  -XX:G1HeapWastePercent=5 -XX:G1MixedGCCountTarget=4 -XX:InitiatingHeapOccupancyPercent=15 \
  -jar server.jar nogui

Set -Xms and -Xmx to the same value, and never give the JVM more than ~80% of the machine's RAM — the OS and off-heap memory need the rest.

Let the calculator do the math

Plug your modpack and player count into the free RAM calculator and it'll suggest a sensible amount plus ready-to-paste flags. It'll often tell you that you need less than you thought — which is the honest answer.

And if you'd rather not run the math at all: on ChunkyHost the server hibernates when nobody's on, so an over-provisioned month doesn't cost you for hours nobody played.