Can I Run Llama 4.5 on Mac Studio (M3 Ultra, 256 GB)?
Written by Jakub Rusinowski · Last updated June 26, 2026
Yes — comfortably
Yes, comfortably — Llama 4.5 Scout at Q8_0 needs about 119.4 GB of the 192 GB usable on Mac Studio (M3 Ultra, 256 GB), leaving ~72.6 GB spare and running at ~21.6 tok/s (estimated), with room for about 131,072 tokens of context.
Confidence: medium · Recommended quantization: Q8_0 · Estimated speed: ~21.6 tok/s
Mac Studio (M3 Ultra, 256 GB) — what it gives a model
| Usable memory for models | 192 GB |
| Memory bandwidth | 819 GB/s |
| Form factor | Desktop |
| Operating system | macOS |
| Memory upgradeable | No — soldered |
Llama 4.5 on Mac Studio (M3 Ultra, 256 GB): memory by quantization
| Quant | Memory needed | Fits 192 GB? | Max context | Est. speed | Download |
|---|
| F16 | 221.6 GB | ✗ No | — | — | 218 GB |
| Q8_0 | 119.4 GB | ✓ Yes | 128K | ~21.6 tok/s | 115.8 GB |
| Q6_K | 92.9 GB | ✓ Yes | 256K | ~26.9 tok/s | 89.4 GB |
| Q5_K_M | 80.8 GB | ✓ Yes | 256K | ~30.4 tok/s | 77.3 GB |
| Q4_K_M | 69.4 GB | ✓ Yes | 256K | ~34.6 tok/s | 65.8 GB |
| Q3_K_M | 50 GB | ✓ Yes | 256K | ~45 tok/s | 46.5 GB |
| Q2_K | 39.4 GB | ✓ Yes | 256K | ~54 tok/s | 35.8 GB |
What to watch out for
- This model does not publish its full attention configuration, so the KV-cache share of these figures is inferred from its parameter count rather than computed exactly.
- Memory on this machine is not upgradeable, so the configuration you buy is the ceiling for every model you will ever run on it.
Mac Studio M3 Ultra 256 GB limitations
- The largest single-box unified memory pool available, but at roughly half the memory bandwidth of a high-end discrete GPU — very large models load, then run slowly.
- Memory is soldered; the configuration chosen at purchase is permanent.
Recommended setup
Ollama or LM Studio (Metal) — MLX for the fastest Apple-native throughput
How these numbers are calculated
- Memory need = quantized weights + KV cache at 8,192 tokens (f16) + 0.8 GB runtime overhead.
- 256 GB unified memory at 819 GB/s, shared between CPU and GPU.
- macOS reserves a share of unified memory for the system, so not all of it is available to a model.
- Throughput is a memory-bandwidth roofline estimate, not a measurement. It is labelled "estimated" everywhere it appears.
- KV cache is inferred from the parameter count because this model does not publish its full attention configuration.
FAQ
Can I run Llama 4.5 on Mac Studio (M3 Ultra, 256 GB)?
Yes, comfortably — Llama 4.5 Scout at Q8_0 needs about 119.4 GB of the 192 GB usable on Mac Studio (M3 Ultra, 256 GB), leaving ~72.6 GB spare and running at ~21.6 tok/s (estimated), with room for about 131,072 tokens of context.
Which quantization of Llama 4.5 should I use on Mac Studio (M3 Ultra, 256 GB)?
Q8_0 — it needs about 119.4 GB of the 192 GB available, downloads as roughly 115.8 GB, and runs at an estimated 21.6 tokens/sec with up to 128K of context.
What limits Llama 4.5 on Mac Studio (M3 Ultra, 256 GB)?
Nothing binding — the model fits with headroom and generates at a usable speed on this hardware.
Which runtime should I use?
Ollama or LM Studio (Metal) — MLX for the fastest Apple-native throughput
Other Computers
Other Models on Mac Studio (M3 Ultra, 256 GB)
Llama 4.5 on GPUs
What This Model Is Good At
Model & Tools
← Can I Run It? | Llama 4.5 model page | Check your hardware