Best LLMs for Mac Studio M3 Ultra (512GB) in 2026 — ranked by measured file sizes
Every pick below comfortably fits Mac Studio M3 Ultra (512GB) at the listed quant with 8K context. Ranking = largest model (more capable) that still fits, ties broken by real download counts. Sizes are measured GGUF files from Hugging Face, updated daily — not formula estimates.
| Model | Params | Best quant that fits | VRAM needed | Downloads |
|---|---|---|---|---|
| Kimi-K2.5 | 1027B | UD-IQ1_S | 332.6 GB | 6k |
| Kimi-K2-Thinking | 1027B | UD-IQ1_S | 343.9 GB | 4k |
| Kimi-K2-Instruct | 1027B | UD-IQ1_S | 337.6 GB | 44k |
| GLM-5.3 | 754B | UD-IQ3_XXS | 339.5 GB | 492k |
| GLM-5.2 | 754B | UD-IQ3_XXS | 339.5 GB | 355k |
| deepseek-v4 | 403B | Q2KDown-AProjQ8-SExpQ8-OutQ8 | 118.6 GB | 1955k |
| GLM-5.3-Flash | 321B | UD-Q6_K_XL | 351.7 GB | 629k |
| Inkling-Small | 264B | UD-Q8_K_XL | 347.6 GB | 1422k |
| Qwen3.8-Flash-Next | 177B | Q8_0 | 227.4 GB | 1525k |
| Qwen3.8-27B-Heretic-Abliterated-Uncensored | 54B | Q8_0 | 139.8 GB | 1828k |
| Qwen3.8-35B-A3B-Distill | 36B | BF16 | 86.8 GB | 28k |
| Ornith-1.5-35B-A3B | 36B | BF16 | 86.8 GB | 4594k |
Leaves ~8% headroom for fragmentation. Long contexts (>8K) grow the KV cache — open the model page for exact math. On Macs the budget is ~75% of unified memory (macOS default GPU limit — adjustable via sysctl iogpu.wired_limit_mb).
How we pick
A model qualifies when its measured GGUF file plus KV cache plus runtime overhead stays under 384GB x 0.92. We choose the largest such quant (bigger quant = less degradation), then rank models by parameter count — at Mac Studio M3 Ultra (512GB) the best model you can run is almost always the largest one that still fits. MoE models count their total size (all experts live in memory), not just active params.