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Tools / LLM GPU calculator / 256 GB Mac Studio

What LLMs can run on a 256 GB Mac Studio?

Which of 22 open LLMs fit one 256 GB Mac Studio, and how many it takes for the rest, at FP16, FP8 and 4-bit.

Size your own scenario

Short answer

One 256 GB Mac Studio (about 192 GB usable by the GPU) runs 18 of the 22 open LLMs sized here at 4-bit, 17 at FP8 and 15 at FP16, for one user at an 8K context. At 4-bit: every model except Llama 3.1 405B, Llama 4 Maverick, DeepSeek-V3 / R1 and GLM-5.3. The largest that fits one Mac is Qwen3-235B-A22B (235.1B parameters), at 4-bit. Bigger models split their layers across several Macs: Llama 4 Maverick takes 2 at 4-bit.

Updated . One user, 8K context, KV cache at FP16, plus 10% headroom for activations and the runtime.

Every model on the 256 GB Mac Studio

ModelFP16/BF16FP84-bit (INT4)
Llama 3.1 8B1 Mac19 GB1 Mac10 GB1 Mac6.1 GB
Qwen3 8B1 Mac20 GB1 Mac10 GB1 Mac6.3 GB
Qwen3 14B1 Mac34 GB1 Mac18 GB1 Mac11 GB
Phi-4 14B1 Mac35 GB1 Mac18 GB1 Mac11 GB
gpt-oss-20b1 Mac47 GB1 Mac23 GB1 Mac13 GB
LFM2.5-24B-A2B1 Mac54 GB1 Mac27 GB1 Mac15 GB
Mistral Small 3.2 24B1 Mac55 GB1 Mac28 GB1 Mac16 GB
Gemma 3 27B1 Mac62 GB1 Mac32 GB1 Mac18 GB
Qwen3-30B-A3B1 Mac69 GB1 Mac35 GB1 Mac20 GB
Qwen3 32B1 Mac75 GB1 Mac39 GB1 Mac22 GB
Qwen2.5 32B1 Mac75 GB1 Mac39 GB1 Mac22 GB
Mixtral 8x7B1 Mac105 GB1 Mac53 GB1 Mac30 GB
Llama 3.3 70B1 Mac160 GB1 Mac81 GB1 Mac46 GB
Qwen2.5 72B1 Mac165 GB1 Mac84 GB1 Mac47 GB
Kolibri-11 Mac174 GB1 Mac87 GB1 Mac48 GB
Llama 4 Scout2 Macs243 GB1 Mac122 GB1 Mac68 GB
gpt-oss-120b2 Macs260 GB1 Mac130 GB1 Mac72 GB
Qwen3-235B-A22B3 Macs524 GB2 Macs263 GB1 Mac145 GB
Llama 4 Maverick5 Macs894 GB3 Macs448 GB2 Macs247 GB
Llama 3.1 405B5 Macs907 GB3 Macs456 GB2 Macs253 GB
DeepSeek-V3 / R18 Macs1,492 GB4 Macs746 GB3 Macs411 GB
GLM-5.39 Macs1,654 GB5 Macs827 GB3 Macs455 GB

Counts are for a layer split, which works with any number of Macs. Below each count is the memory needed: (weights + KV cache) ÷ 0.9. Capacity only: speed depends on memory bandwidth and the serving stack.

Memory is step one. Throughput, latency, power and the network decide the real build.

Size my actual workload

256 GB Mac Studio specifications

Memory
256 GB unified, about 192 GB usable by the GPU
Memory bandwidth
819 GB/s
Typical system
Desktop
Counted as
Layer split across cards (llama.cpp style)

Questions about the 256 GB Mac Studio

What LLMs can run on a 256 GB Mac Studio?

For one user at an 8K context, these fit one 256 GB Mac Studio. At 4-bit: every model except Llama 3.1 405B, Llama 4 Maverick, DeepSeek-V3 / R1 and GLM-5.3. At FP8: every model except Llama 3.1 405B, Llama 4 Maverick, Qwen3-235B-A22B, DeepSeek-V3 / R1 and GLM-5.3. At FP16/BF16: every model except Llama 3.1 405B, Llama 4 Scout, Llama 4 Maverick, Qwen3-235B-A22B, DeepSeek-V3 / R1, gpt-oss-120b and GLM-5.3. That counts the 192 GB of unified memory macOS lets the GPU use by default.

What is the largest LLM a 256 GB Mac Studio can run?

Of the models sized here, for one user at an 8K context: at 4-bit, Qwen3-235B-A22B (235.1B parameters, 145 GB); at FP8, gpt-oss-120b (116.8B parameters, 130 GB); at FP16, Kolibri-1 (78.1B parameters, 174 GB). Mixture-of-experts models count every expert, because all of them must be in memory.

How many 256 GB Mac Studios does Llama 3.3 70B need?

For one user at an 8K context it needs 160 GB at FP16/BF16, 81 GB at FP8 and 46 GB at 4-bit: one Mac at FP16, FP8 or 4-bit.

Can a 256 GB Mac Studio run DeepSeek-V3 / R1?

Not on one Mac: with all 671B parameters resident it needs 746 GB at FP8 and 411 GB at 4-bit for one user at an 8K context. That is 4 Macs at FP8 and 3 Macs at 4-bit, with a layer split.

Can I combine several 256 GB Mac Studios?

Yes, with a layer split: each Mac holds some of the model's layers, as llama.cpp does. Memory adds up across them; speed does not, because they take turns on each token. The counts on this page assume a layer split.

Other GPUs

Different context length, more users, or a model that isn’t listed? The LLM GPU calculator sizes any Hugging Face model for any of these GPUs.

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