Can MacBook Pro M3 Pro 18 GB run gpt-oss-20b?
18 GB unified · 150 GB/s memory bandwidth · gpt-oss-20b has 20.9B parameters (3.6B active per token).
Short answer
No. It doesn't fit in memory.
Needs ≈12 GB but only ≈11 GB is available after the OS, other apps and Open WebUI.
Why it doesn’t fit
Even its smallest practical version (MXFP4) needs about 12 GB for the model, its context memory and the runtime. After macOS (≈3.5 GB), a browser with a few tabs (≈3.0 GB) and Open WebUI (≈1.0 GB), MacBook Pro M3 Pro 18 GB has about 11 GB left, so it’s 1.8 GB short.
Ways to make it work
Close everything else
With no other apps open, gpt-oss-20b runs at MXFP4: Acceptable at 35–45 tok/s. Expect the system to feel tight while it’s loaded.
Pick a smaller model from the same family
No smaller gpt-oss model in our catalog runs well here. See the other models below.
Get more memory
The same chip with 36 GB handles it: Excellent.
Check your exact setup
These pages assume typical settings. A shorter context or a lighter chat app can change the answer.
Check MacBook Pro M3 Pro 18 GB
The same applies to every workload we rate (chat, coding questions, coding in a repository, agentic coding and long documents): they all need at least as much memory as chat.
Other models for MacBook Pro M3 Pro 18 GB
The best-rated models for chat on this machine.
- MiniCPM5 2B35–45 tok/sExcellent
- Qwen3.5 4B25–30 tok/sExcellent
- Llama 3.2 3B Instruct30–45 tok/sExcellent
- Qwen3 8B19–25 tok/sExcellent
- Gemma 4 E4B20–30 tok/sExcellent
- DeepSeek-R1-0528-Qwen3-8B19–25 tok/sExcellent
Cheapest machines for gpt-oss-20b
Hardware rated comfortable or better for chat, lowest price first.
- Mac mini M4 24 GB$999 · 25–35 tok/sExcellent
- Mac mini M6 24 GB$1,299 · 30–50 tok/sExcellent
- Laptop · Ryzen AI 9 HX 370 (Radeon 890M) · 32 GB$1,300 · 20–35 tok/sExcellent
- Laptop · Core Ultra 7 258V (Arc 140V) · 32 GB$1,300 · 18–30 tok/sExcellent
- Desktop PC · GeForce RTX 5060 Ti 16GB · 32 GB RAM$1,330 · ≈100 tok/sExcellent
- Desktop PC · GeForce RTX 4060 Ti 16GB · 32 GB RAM$1,350 · 50–85 tok/sExcellent
Same chip, other memory: 36 GB
Different tool, context size or workload?
These pages use typical settings. The full check models your exact setup.