Everything is spot on, exactly what you want
The service, the servers, it's nothing but fantastic. Will help you with whatever it is, even if you're slow like me they help amazingly and keep their cool. Nothing but love for the guy, an amazing soul.
DayZ loads the whole map and its central economy, the loot and vehicles across it, before anyone joins, which is why it needs more memory than most games from the start.
Mods are what push it up from there. Vehicle, weapon and building packs and big frameworks like Expansion add a lot, and more players mean more bases, vehicles and stashes to track.
The calculator adds those up from data we collected on DayZ servers, then leaves about 15% headroom so the server never runs right at its limit. It's a guide, not a promise, and you can upgrade from the client area at any time.
Quick answers about DayZ server memory.
8 GB runs vanilla and most modded servers well, even with around 100 mods. Busy modded servers want 12 GB, and very busy servers with big content mods or Expansion need 16 GB.
Yes, big content mods do. Vehicle and weapon packs and frameworks like Expansion are the heaviest.
A little more than Chernarus or Livonia, since maps like Deer Isle or Namalsk carry more to load.
It is an estimate based on data we collected, with headroom added. You can upgrade from the client area at any time.