Can I Run GPT-OSS on Apple M3?
Written by Jakub Rusinowski · Last updated August 15, 2026
Yes, comfortably — GPT-OSS 20B at MXFP4 needs 12.3 GB at 8K context (11.1 GB weights + 1.2 GB KV cache/overhead), leaving ~5.7 GB of the Apple M3's 18 GB usable memory, at ~24 tok/s (est.).
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Apple M3 Specs
| VRAM | 24 GB unified memory |
| Memory Bandwidth | 100 GB/s |
GPT-OSS 20B on the Apple M3: VRAM by quantization
| Quant | VRAM needed | Fits 24 GB? | Max context | Whole PC |
|---|---|---|---|---|
| F16 | 43 GB | ✗ No | — | — |
| Q8_0 | 23.4 GB | ✗ No | — | — |
| Q6_K | 18.3 GB | ✗ No | — | — |
| Q5_K_M | 16 GB | ✓ Yes | 32K | — |
| Q4_K_M | 13.8 GB | ✓ Yes | 64K | — |
| Q3_K_M | 10.1 GB | ✓ Yes | 128K | — |
| Q2_K | 8.1 GB | ✓ Yes | 128K | — |
Assumes an 8K-token context with an f16 KV cache. A longer window needs more; a quantized KV cache needs less. “Max context” is the largest window that still fits in 24 GB of unified memory. Figures are estimates from parameter count, quantization and memory bandwidth — the analyzer lets you tune KV-cache quant and context.
Context costs VRAM too. At MXFP4 on the Apple M3: 8K 12.3 GB · 32K 13.5 GB · 128K 18.3 GB ✗. Past 128K it no longer fits 24 GB — a q8_0 KV cache buys roughly half of that back, which the calculator will price for you.
No compatible GPU? GPT-OSS 20B on 16 GB of system RAM, CPU only: runs.
GPT-OSS Sizes That Fit the Apple M3 (at 8K context)
| GPT-OSS 20B | MXFP4 · 12.3 GB at 8K context · ~24 tok/s (est.) |
GPT-OSS needs ~12 GB but this GPU has 24 GB. Rent a RTX 4090 (24 GB)-class GPU by the hour instead of buying one:
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Cloud rates verified 2026-07 — estimates, and marketplace prices vary. Buying price is GPU MSRP only, not a full PC.
FAQ
Can I run GPT-OSS on the Apple M3?
Yes, comfortably — GPT-OSS 20B at MXFP4 needs 12.3 GB at 8K context (11.1 GB weights + 1.2 GB KV cache/overhead), leaving ~5.7 GB of the Apple M3's 18 GB usable memory, at ~24 tok/s (est.).
What's the best GPT-OSS size for the Apple M3?
GPT-OSS 20B at MXFP4 quantization needs 12.3 GB at 8K context (11.1 GB weights + 1.2 GB KV cache/overhead), estimated ~24 tokens/sec.
Every GPT-OSS size on the Apple M3
| Size | VRAM at 8K | Verdict | Speed |
|---|---|---|---|
| GPT-OSS 120B | 71.9 GB | Does not fit | — |
| GPT-OSS 20B | 12.3 GB | Runs | ~24 tok/s |
GPT-OSS on Other GPUs
- GPT-OSS on NVIDIA GeForce RTX 4090
- GPT-OSS on NVIDIA GeForce RTX 3090
- GPT-OSS on AMD Radeon RX 7900 XTX
- GPT-OSS on Apple M4 Pro
- GPT-OSS on Apple M2
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