LLM VRAM Calculator
Estimate the VRAM (GPU memory) needed to run an LLM locally, from model size, quantization, and context length — and see at a glance which GPUs and Macs can handle it. Free, no sign-up.
Pick your setup — the estimate updates instantly
Estimated VRAM required
22.6 GB
Breakdown: ~18.8GB weights (31B × Q4_K_M (4bit)) + KV cache & buffers at 16K context
GPUs that fit
- RTX 3090 / 4090 (24GB)
- RTX 5090 (32GB)
- RTX A6000 (48GB)
- A100 / H100 (80GB)
Macs that fit (unified memory)
- Mac 32GB (M1〜M4)
- Mac 64GB (M1〜M4 Pro/Max)
- Mac 128GB (M3/M4 Max)
- Mac Studio 192GB (Ultra)
Estimates only — actual usage varies ±10-20% by runtime (llama.cpp / Ollama / vLLM / MLX) and settings. Models exceeding VRAM can often still run slowly via RAM offloading. Mac unified memory is counted at ~75% of total as usable.
For per-model details, see Gemma 4 Requirements and Qwen3.5-9B Local Setup.