1 - Players and distances
Every chunk inside the view distance is loaded and held in memory; the simulation distance decides which of them tick mobs and crops, so it drives CPU far more than memory. Both default to 10.
Each player loads their own square of chunks: the most a server ever holds for this count. Survival servers live near this.
2 - What else you run
Nobody can measure your modpack from here. Read it off your own server: run it with the mods and no players, trigger a garbage collection (a profiler, or /paper heap on Paper) and take the used heap, minus the 132 MB a bare server holds.
Paper's advice for a hosting plan: set Xmx 1500 MB under the plan size, because the JVM, the panel and the operating system all need room the plan does not mention.
Set -Xmx to
Paper's own advice is at least 6 GB whatever the player count, because G1 runs smoother with room. Your plan has it, so there is no reason to go lower than that.
Start command
java -Xms2560M -Xmx2560M -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 -Dusing.aikars.flags=https://mcflags.emc.gs -Daikars.new.flags=true -jar server.jar --nogui
Aikar's flags from the Paper docs, with Xms set equal to Xmx the way they recommend. Replace server.jar with your jar. Drop --nogui on a vanilla jar, which spells it nogui.
Where the numbers come from
A vanilla 26.3 server on Java 25 with a 6 GB G1 heap, a fresh world and no players, measured after a full garbage collection: 132 MB with only the spawn chunks loaded, 438 MB with 1,024 force-loaded chunks and 1,155 MB with 4,096. That is 250 KB a chunk on the big run and 300 KB on the small one; the calculator uses 250. Players, entities, redstone and plugins all add to it, which is what the working room and the extra field are for.
What a server spends memory on
Loaded chunks. A chunk holds its blocks, its lighting, its block entities and its mobs, and the server keeps every chunk inside every player's view distance resident. The bare server, with its registries and the spawn chunks, is small by comparison, and players themselves cost almost nothing. So the memory question is really: how many chunks, times how much each.
Hosting companies answer that question with plan sizes, which is the wrong way round. This page answers it from a measured server: the numbers in the panel above are what a 26.3 server actually held after a full garbage collection with a known number of chunks loaded. From there the arithmetic is honest: chunks a player loads times players (or once, if they stay together), times the measured cost, plus the bare server, plus whatever your mods add, which you measure the same way on your own machine.
Working room and the plan ceiling
A heap sized exactly to the live set thrashes the collector, so the recommendation doubles it and never goes under 2 GB. Aikar's flags assume that kind of room: they reserve 20 percent of the heap and want a young generation of 30 to 40 percent. The other direction is the one that crashes servers. The JVM needs memory outside the heap, and on a hosting plan the panel and the system come out of the same allowance, which is why Paper tells you to set Xmx 1000 to 1500 MB under the plan size. The plan check here uses that reserve.
Frequently Asked Questions
How much RAM does a Minecraft server need?
For a vanilla or Paper server, roughly 130 MB for the server itself plus a quarter of a megabyte per loaded chunk, doubled for garbage collection room, and never under 2 GB. Ten players spread out at view distance 10 load 4,410 chunks, about 1.1 GB live, so a 2.5 to 3 GB heap. Paper recommends at least 6 GB if the host has it, because G1 collects more smoothly with room. Mods are on top of all that, and only your own server can tell you how much.
How much RAM per player?
It is not per player, it is per loaded chunk, and a player loads (2 x view distance + 1) squared chunks: 441 at view distance 10, 1,089 at 16, 169 at 6. At 250 KB a chunk that is 110 MB per spread-out player at the default distance, and far less when players are together, because they share one loaded area.
Does view distance or simulation distance use more RAM?
View distance. Every chunk inside it is loaded and held in memory whether it ticks or not. Simulation distance only decides which of those chunks run mobs, crops and redstone, which is CPU. Dropping view distance from 10 to 8 cuts a spread-out server's chunk memory by a third; dropping simulation distance saves tick time, not memory.
Should Xms be the same as Xmx?
Yes with Aikar's flags, which is what Paper recommends. G1 handles a large heap well and memory the JVM is allowed but not given is wasted, so the flags set both to the same number and pre-touch the whole heap at start. The one case against it is a machine too small for the heap, which the calculator's plan check is for.
Why did my server crash with out of memory on a 4 GB plan?
Because Xmx was set to the plan size. The heap is not the only memory the JVM uses: metaspace, thread stacks, Netty buffers and the garbage collector's own bookkeeping sit outside it, and the host's panel and operating system need some too. Paper's advice is to set Xmx 1000 to 1500 MB below what the plan says, which is what the shared host option here does.
Where do the 250 KB and 132 MB come from?
A measurement, not a rule of thumb: a vanilla 26.3 dedicated server on Java 25 with a 6 GB G1 heap and a fresh world, no players, measured after a forced full garbage collection. Spawn chunks only: 132 MB. 1,024 force-loaded chunks: 438 MB. 4,096: 1,155 MB. That is 250 KB a chunk on the big run and 300 KB on the small one, for chunks loaded at full ticking level the way a player's view distance loads them.
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