Realistic GPU/Memory Sizing for Local LLMs

Decision-first: Budget file size + KV(context) + overhead, not file size — and on unified memory, subtract OS + co-resident workloads first. “Barely fits” means doesn’t fit. Size memory by total params, speed by active params.

Scope & freshness: General sizing principles (version-independent); worked numbers from 2026-05 on a GB10 (128 GB unified) + a 64 GB Apple-Silicon Mac. Re-measure resident sizes for your model/quant/context.

Resident size is bigger than the file#

The single most common sizing mistake is equating the model file size with how much memory it needs at runtime. Resident footprint is:

Ollama Setup and Model Management: Installation, Model Selection, Memory Management, and ARM64 Native

Ollama Setup and Model Management#

Ollama turns running local LLMs into a single command. It handles model downloads, quantization, GPU memory allocation, and exposes a REST API that any application can call. No Python environments, no CUDA driver debugging, no manual GGUF file management.

Installation#

# macOS
brew install ollama

# Linux (official installer)
curl -fsSL https://ollama.com/install.sh | sh

# Or run as a Docker container
docker run -d -v ollama:/root/.ollama -p 11434:11434 --name ollama ollama/ollama

Start the Ollama server: