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Memory budget · 256 GB

Best local LLMs for 256GB

The Apple M3 Ultra (256GB) gives about ~192 GB of its 256GB to model weights after the OS takes its share. 121 of 135 local LLMs fit, biggest first.

Usable range
192–192 GB
Models that fit
121
Memory types
1
Top pick
235B

What 256GB actually gives you

Usable figures are sourced per device (tap a card for the full profile). Verdicts below use Q4_K_M, the community-default quant.

Top pick for 256GB Q4_K_M

Runs comfortably on the most capable 256GB setup (Apple M3 Ultra (256GB), ~192 GB usable) at ~136.9 GB. Check it against your exact device on its model page.

Models ranked for 256GB

Biggest that fits first Mac

Each chip links to the full breakdown for that model on a real 256GB device. "Tight" means it fits but with little headroom, close other apps.

The ceiling, per memory type

Apple M3 Ultra (256GB) (~192 GB usable)

Runs up to Qwen3 235B A22B (235B) comfortably at Q4_K_M. Larger models either sit tight or spill past the ~192 GB it can give a model.

FAQ

How much of 256GB can a model actually use?

It depends on the memory type. Apple unified memory: about 192 GB (Apple M3 Ultra (256GB)). The rest is reserved for the OS, display and runtime overhead.

What is the best local LLM for 256GB?

Qwen3 235B A22B (235B) is the strongest model that runs comfortably at Q4_K_M on the most capable 256GB setup (Apple M3 Ultra (256GB), ~192 GB usable). On a tighter 256GB device the ceiling is lower, shown per row above.

Sources

Memory figures are estimates at Q4_K_M with a small context. See methodology.