How to use the RAM calculator
- Choose your edition. Java servers run on Java and use
-Xmx. Bedrock Dedicated Server is a native program, so the calculator shows the free memory to plan for instead. - Pick the server software and how many plugins or mods you run. Paper and Spigot use plugins; Fabric, Forge and NeoForge use mods.
- Set the players you expect online at the same time, not the total number of people who ever join.
- Match your distances to
view-distanceandsimulation-distanceinserver.properties(on Bedrock,view-distanceandtick-distance). - Extra worlds means additional worlds kept loaded beyond the usual Overworld, Nether and End, for example a separate creative or resource world on a multi-world plugin.
- Copy the start command into your
start.batorstart.sh. New to servers? Follow how to make a Minecraft server first.
Typical results
These are the calculator's ranges at the default view and simulation distance. Use them as a quick check, then fine-tune with your own settings above.
| Server | Players | Allocate (-Xmx) |
|---|---|---|
| Vanilla Java | 1–10 | 2–3 GB |
| Vanilla Java | 20 | 3–4 GB |
| Paper, 15–40 plugins | 10 | 3–4 GB |
| Paper, 15–40 plugins | 20 | 4–5.5 GB |
| Paper, 40+ plugins | 50 | 6.5–8.5 GB |
| Fabric, under 50 mods | 5 | 2.5–4 GB |
| Fabric, 50–150 mods | 10 | 4.5–6 GB |
| Forge / NeoForge, 50–150 mods | 5 | 6–7.5 GB |
| Forge / NeoForge, 150–300+ mods | 10 | 8.5–11 GB |
| Bedrock Dedicated Server | 10 | 1.5–2.5 GB free RAM |
The player count is the number online at the same time. Ten friends who log in at different times of day need far less than ten players exploring in ten directions at once, because every player who travels away from the others loads a fresh area of chunks.
How we estimate
Mojang does not publish a RAM formula for servers, and real usage depends on how far apart players are, what they build and which mods you run. This calculator uses a simple, visible model built from common community guidance, tuned so that the results match well-known reference points:
- The Minecraft Wiki's server tutorial suggests
-Xmx2Gfor a home server with about five players on default settings. Our vanilla, 5-player result is 2–3 GB. - Mojang's Bedrock server page says at least 1 GB is enough for small worlds.
- Large Forge and NeoForge modpacks commonly ask for 6 to 10 GB or more; our heavy modpack tier lands there.
| Part | Value used | Why |
|---|---|---|
| Base | 1 GB vanilla, 1.25 GB Paper, 1.5 GB Fabric, 2 GB Forge/NeoForge, 0.75 GB Bedrock | Java itself, the server code, the mod loader and the area around spawn. |
| Per player | 100 MB (Fabric 125 MB, Forge 150 MB, Bedrock 80 MB) at default distances | Each player keeps their own area of chunks, entities and data loaded. Players beyond 20 count at 50% because crowds share chunks. |
| Distance factor | Java: 70% view distance + 30% simulation distance, each as (chunks ÷ 441)0.6. Bedrock: 50% view (against 32) + 50% tick distance (against 4) | The loaded area grows with the square of the distance: 10 means 21 × 21 = 441 chunks, 16 means 1,089. The 0.6 exponent damps this, because outer chunks are cheaper than busy ones and nearby players share chunks. View 16 gives ×1.5, view 6 gives ×0.69. |
| Plugins / mods | Paper +0.25 / 0.75 / 1.5 GB; Fabric +0.5 / 1.75 / 3.5 GB; Forge +1 / 3 / 5 GB | Mods add blocks, items, recipes and logic that stay in memory; plugins are lighter. |
| Extra worlds | +400 MB each | Each loaded world keeps its own chunks and data. |
| Range | Estimate to estimate × 1.25 + 0.25 GB, minimum 2 GB (Java) | Headroom for busy moments, exploration and garbage collection. |
The machine or PC memory adds Java's own overhead on top of -Xmx: the Paper docs advise keeping about 1000 to 1500 MB free for the operating system and Java, so on an 8 GB host you would set about 6.5 GB. If you also play on the same PC, the calculator adds Mojang's 8 GB minimum for playing Java Edition.
RAM, CPU and garbage collection
RAM only needs to be big enough. Once the server has room to breathe, more memory does not add speed. Minecraft's game logic runs mostly on one main server thread, so a CPU with fast single-core performance is what keeps the server at 20 ticks per second. If the server lags with plenty of free memory, lower the view and simulation distance, switch to Paper and pregenerate the world before buying more RAM.
Too much RAM can even hurt. Java frees memory with a garbage collector, and very large heaps can lead to longer pauses, which players feel as lag spikes. When you self-host, every gigabyte you give the server is taken from your operating system and game; if the PC runs out and starts swapping to disk, everything stutters.
The Paper docs recommend setting -Xms equal to -Xmx and suggest 6 to 10 GB as a comfortable target for their tuned setup. That is a performance target for busy Paper servers; a small private server runs fine on less.
Aikar's flags
Aikar's flags are a set of garbage-collection settings for the G1 collector, published and explained in the Paper documentation. Tick the box above to add them; they set -Xms and -Xmx to the same value. They are optional. If a modpack ships its own JVM arguments, start with those.