The Math Behind Local LLMs: How to Calculate Exact VRAM Requirements Before You Crash Your GPU

If you’ve spent any time in the open-source AI community recently, you’ve probably seen someone excitedly announce they are running a 70B parameter model locally, only to follow up an hour later asking why their system crashed with an OOM (Out of Memory) error. Deploying Large Language Models (LLMs) locally—whether for privacy, cost savings, or offline availability—is the new frontier for developers. But unlike deploying a standard web app where you just spin up an AWS EC2 instance and forget ab