RAM calculator
How much memory to give Minecraft for your pack and your PC.
Recommended allocation
6 GB
How we calculate it: about 2 GB for the game plus around 25 MB per mod, more for big content mods, +1 GB for shaders and +1 GB above 16 chunks of render distance. We cap at 12 GB because bigger heaps mostly add pauses, and always leave 3 GB for your system.
This is a starting point. If the F3 memory reading sits near 100%, add 1 GB; if it never passes 60%, you can lower it.