How Much RAM Does Your Modpack Server Need?

A vanilla or Paper server runs perfectly happily on 1 to 2 GB of RAM. A light modpack of up to roughly 60 mods needs 4 GB, a mid-sized pack of 100 to 200 mods wants 6 to 8 GB, and a big kitchen-sink pack with 300 mods or more, such as All the Mods 10, only really gets going at 10 to 12 GB. The number of mods sets the floor; players stack on top of that at roughly 1 to 2 GB per extra handful of players once heavy automation gets involved.

Why does the mod count weigh more than the player count?

On startup, a modded server loads everything the pack brings with it into memory: every block, every item, every recipe, every entity type, every biome and every dimension. That happens even with nobody online. An idling server with a big pack therefore already needs almost its entire memory budget. All the Mods 10 sits at 400 to 500 mods, and those registries are a fixed cost you cannot shrink by letting fewer players in.

Players are the variable cost on top. Every player loads chunks around themselves, including the entities and running machines inside them. Four friends building together in the same valley cost very little extra. Four players each with their own factory in their own corner of the map, with chunk loaders ticking away while they are offline, cost considerably more. Hence the rule of thumb of 1 to 2 GB per extra handful of players once automation gets heavy.

That works both ways. If you want to run ATM10 for two people, you are not doing yourself any favours with 6 GB. If you run a Paper server with plugins and fifty players, you usually do not need 16 GB at all; that server has a CPU problem far sooner than a memory problem.

How much RAM do you need per type of server?

These figures are about the server, not about your own PC. Some packs are lighter than their reputation suggests: Cobblemon packs often run fine on 4 to 8 GB, while old Pixelmon servers offering much the same kind of gameplay frequently needed 10 to 12 GB. So check the pack author's recommendation first. If you are still unsure how a pack is put together, read up on what a modpack actually is and how you install one.

Can too much RAM be harmful?

Yes, and that surprises a lot of people. Java does not clear memory straight away; it lets rubbish pile up and clears it periodically with the garbage collector. The bigger the heap, the more the collector has to walk through when its turn comes. Hand a pack that needs 6 GB a great deal more than that and the rubbish sits around longer, making each clean-up heavier. The result is not higher TPS, but the occasional noticeable stutter.

More RAM is not a speed slider, then. It is a ceiling that has to be high enough that you never hit it, and not a great deal higher. If your server crashes with an OutOfMemoryError, it needs more memory. If usage stays comfortably below the ceiling after a clean-up, extra gigabytes only buy you longer pauses and a bigger bill.

What do Xmx and Xms actually mean?

-Xmx is the maximum heap size: the ceiling Java will never go past. -Xms is the heap size Java starts with. Set -Xms low and the server starts small and grows in steps, which creates extra work while a big pack is booting.

1. Check how much RAM your package has. That is your upper limit, because alongside the heap the Java process also uses memory for threads and network buffers.
2. So set -Xmx just under the package size: on an 8 GB package you do not give the heap the full 8 GB.
3. Set -Xms to the same value as -Xmx, so the heap is not constantly growing and shrinking.
4. Restart the server and let it run for an hour with players on it. The first few minutes after a restart tell you very little.
5. Then look at the memory graph in your panel. If usage settles at roughly the same level after every clean-up, you are in good shape. If the line keeps grazing the ceiling, you either need more RAM or one mod fewer.

In the Pterodactyl panel you set this in the startup variables, so you never have to touch a start script. If you are not certain how your server is put together, our guide on how to make a Minecraft server yourself will help.

Why do pregeneration and view-distance matter more than an extra gigabyte?

The most expensive thing a modded server does is generate new world. A big pack adds extra structures, ores and sometimes whole dimensions to that, all calculated the moment a player crosses a boundary. That is precisely when your server stutters: someone flies over unexplored terrain with an elytra and the TPS drops away. Extra RAM does not fix that, because the problem is computation, not space.

The fix is to generate the world in advance with a pregeneration tool before you let players in. Your server works the chunks out during a quiet moment and writes them to disk, so later on it only has to read them back. Do that per dimension and with a boundary that suits your player count.

The second dial is view-distance in server.properties, the file holding your server's core settings. Every step up increases the number of chunks the server tracks per player, and that scales sharply. Dropping from 10 to 6 does more for a busy modded pack than a couple of extra gigabytes. You can often set simulation-distance one step lower still: players still see a long way, but the server does not have to tick mobs and machines everywhere. Our article on optimising your Minecraft server goes deeper into these settings and into measuring TPS, the ticks per second that show how smoothly your server is running.

Is CPU clock speed not the real bottleneck?

Often it is. Minecraft's world tick runs on a single thread. Everything that happens in a tick (mobs, redstone, machines, hoppers, world generation) is handled one after another, and there are 50 milliseconds for the lot if you want to hit 20 TPS. More cores barely help; what counts is how fast a single core clears that queue. Clock speed therefore matters more to a modded server than core count.

You notice that most with automation packs. A base full of Create machines fills your tick budget without memory usage rising in any meaningful way. If you see low TPS while your RAM usage stays neatly below the ceiling, a bigger package buys you nothing. Measure with spark first to find out which mod or which chunk is eating the tick budget.

At Minecraft hosting from MC-Node the budget line runs on AMD EPYC 7443P and the premium line on AMD Ryzen 9 9950X. For a small pack with friends the budget line is more than enough; if you want a big automation pack to stay smooth with an active group, the faster line is worth the money sooner than a couple of extra gigabytes on the slower one.

How do you cut RAM usage without buying more?

Optimisation mods are the easiest win. On NeoForge, FerriteCore, Canary and ModernFix are the usual picks. FerriteCore on its own typically saves around 30 to 40 percent of memory by merging duplicate blockstate and model data. None of them change the game itself.

Run the right Java version as well: ATM10 requires Java 21 and simply will not start on Java 17. Storage counts too. On a pack like ATM10, an SSD is the difference between well over ten minutes of load time on a hard disk and two to three minutes; an NVMe SSD comes as standard with every package here. Finally, you can look at whether any mods can go. On a pack you assembled yourself that works nicely, but in a kitchen-sink pack recipes and quest lines are woven together, and you break more than you gain.

Frequently asked questions

How much RAM does All the Mods 10 need? At least 10 GB for the server, 12 GB for a small group and 14 to 16 GB once you play with 5 or more players or automate heavily. ATM10 runs on NeoForge for Minecraft 1.21.1 and requires Java 21; Java 17 will not work.

Is 4 GB enough for a modpack? For a light pack of up to roughly 60 mods, 4 GB is enough. Cobblemon packs often run fine on 4 to 8 GB. For a kitchen-sink pack with 300 mods or more, 4 GB is nowhere near enough; it either will not start or crashes within a few minutes.

Will more RAM make my server faster? No. RAM is a ceiling, not an accelerator. Too much heap actually makes garbage collection pauses longer. If your memory usage stays neatly below the ceiling while TPS is low, the problem lies with the CPU, with your view-distance or with one specific mod.

What is the difference between Xmx and Xms? -Xmx is the maximum heap Java is allowed to use, and -Xms is the size the process starts at. On a server doing nothing else you usually set them equal, and both slightly under your package size, because Java also uses memory outside the heap.

What does 8 GB of RAM cost at MC-Node? The budget line costs EUR 1.10 per GB per month, so 8 GB works out at EUR 8.80 per month. At 15 GB the price drops to EUR 1.00 per GB, or EUR 15.00 per month. The premium line with the faster processor costs EUR 2.50 per GB.

Further reading

• Forge, NeoForge, Fabric or Quilt: Which Modloader to Choose?
• Update a modpack without losing your world
• Folia: Multithreaded Minecraft, and Why It Is Not for You Yet