Can GPT-OSS 20B run on iPhone 16 Pro Max?
NO — Won't fit
Grade F · 0/100 · formula estimate
What this means
None of the versions we checked fit safely on this phone. The checked version needs about 14.8 GB, while we estimate that the model can use about 5.2 GB.
Try a smaller model, or use this model on a device with more memory.
This result is calculated from the phone and model specifications. It has not been measured on this exact phone and setup.
−9.6GB short
memory that doesn't exist here
14.8GB
needed at MXFP4
MXFP4
quant checked
F
grade · 0/100
needs 14.8 GBusable 5.2 GB · short 9.6 GB
Apple A18 Pro8 GB RAMMetal
Three ways forward
1
Try a smaller quant
No quant of GPT-OSS 20B fits this phone — even the smallest is too big. Options 2 and 3 are your real choices.
3
Run it in the cloud
The full GPT-OSS 20B, no download, at data-center speed — pay per token.
provider recommendations coming later
Where the memory goes
| Component | Detail | GB |
|---|---|---|
| Model weights | MXFP4 GGUF (12.1 GB) + mmap overhead | 12.7 |
| KV cache | 4K context window | 1.5 |
| Runtime | llama.cpp + app overhead | 0.6 |
| Total needed | at MXFP4, 4K context | 14.8 |
| Usable on iPhone 16 Pro Max | 8 GB RAM − iOS reserve (jetsam limit) | 5.2 |
| Headroom | missing — this memory doesn't exist | −9.6 |
Pick your quant
| Quant | Download | Verdict | Speed |
|---|---|---|---|
| MXFP4 | 12.1 GB | ✕ Won't fit | won't fit |
Related checks
MORE ON IPHONE 16 PRO MAX
GPT-OSS 20B ON OTHER PHONES