NeuroGenesysWhat LLMs can I run on a Mac with 128 GB?
Last updated • By Will Schulz
On a Mac with 128 GB of unified memory you can run 21 of the 24 open-weight models we track with an 8K context. The largest is Qwen3 235B-A22B at 2-bit (Q2_K), which needs 98.5 GB, and 15 run unquantized at 16-bit.
Models that fit a Mac with 128 GB of unified memory
| Model | Best fit | Memory | Longest context | |
|---|---|---|---|---|
| Qwen3 235B-A22B | 2-bit (Q2_K) | 98.5 GB | 16K | calculator |
| gpt-oss-120b | Q6_K | 100 GB | 64K | calculator |
| Llama 4 Scout | Q6_K | 94.8 GB | 128K | calculator |
| Qwen2.5 72B | INT8 / Q8_0 | 83.2 GB | 64K | calculator |
| Llama 3.1 70B | INT8 / Q8_0 | 80.9 GB | 64K | calculator |
| Llama 3.3 70B | INT8 / Q8_0 | 80.9 GB | 64K | calculator |
| Mixtral 8x7B | BF16 / FP16 | 98.3 GB | 32K | calculator |
| Qwen3 32B | BF16 / FP16 | 70.7 GB | 128K | calculator |
| Qwen2.5 32B | BF16 / FP16 | 70.1 GB | 128K | calculator |
| Qwen3 30B-A3B | BF16 / FP16 | 64.6 GB | 128K | calculator |
| Gemma 3 27B | BF16 / FP16 | 58.6 GB | 128K | calculator |
| Gemma 2 27B | BF16 / FP16 | 59.3 GB | 128K | calculator |
| gpt-oss-20b | BF16 / FP16 | 44.5 GB | 128K | calculator |
| Qwen2.5 14B | BF16 / FP16 | 32.9 GB | 128K | calculator |
| Phi-4 (14B) | BF16 / FP16 | 33.0 GB | 128K | calculator |
| Gemma 3 12B | BF16 / FP16 | 27.0 GB | 128K | calculator |
| Gemma 2 9B | BF16 / FP16 | 22.1 GB | 128K | calculator |
| Qwen3 8B | BF16 / FP16 | 19.1 GB | 128K | calculator |
| Llama 3.1 8B | BF16 / FP16 | 18.6 GB | 128K | calculator |
| Qwen2.5 7B | BF16 / FP16 | 17.2 GB | 128K | calculator |
| Mistral 7B v0.3 | BF16 / FP16 | 17.0 GB | 128K | calculator |
Memory is weights + FP16 KV cache + runtime overhead for one request, as in the VRAM calculator, assuming macOS letting the GPU use 75% of unified memory (about 96.0 GB) by default. Longest context is the largest of 4K–128K that fits at that quantization; it is only usable up to the model's own context window.
Models too large for a Mac with 128 GB of unified memory
Even at 2-bit (Q2_K) these need more memory: Llama 3.1 405B, Llama 4 Maverick, DeepSeek-V3 / R1.
Questions
What is the largest LLM that runs on a Mac with 128 GB of unified memory?
Of the models we track, Qwen3 235B-A22B (235B parameters) at 2-bit (Q2_K), which needs 98.5 GB with an 8K context. Larger models need more memory.
Can a Mac with 128 GB of unified memory run a model at full 16-bit precision?
Yes, 15 models: Mixtral 8x7B, Qwen3 32B, Qwen2.5 32B, Qwen3 30B-A3B, Gemma 3 27B, Gemma 2 27B, gpt-oss-20b, Qwen2.5 14B, Phi-4 (14B), Gemma 3 12B, Gemma 2 9B, Qwen3 8B, Llama 3.1 8B, Qwen2.5 7B, Mistral 7B v0.3. Larger models need quantizing, usually to Q4_K_M (about 4.9 bits per weight), which loses little quality.
How much memory does a 128 GB Mac leave for context?
The KV cache grows with every token of context, so the longest context that fits depends on the model and quantization; the table lists it for each model, trying 4K, 8K, 16K, 32K, 64K and 128K tokens. These figures assume macOS letting the GPU use 75% of unified memory (about 96.0 GB) by default.
