What GPU do I need to run unsloth/gpt-oss-20b-BF16?
20.9B parameters, published in BF16. View on Hugging Face
Set up gpt-oss-20b-BF16gpt-oss-20b-BF16 is published by unsloth on Hugging Face, with 96,015 downloads and 34 likes to date. It's a GptOssForCausalLM model built for text-generation, published natively in BF16.
VRAM required & cheapest live GPU fit
Required VRAM = weight size at each precision times a flat 1.2 overhead for activations and fragmentation. The KV-cache grows with context and is not in that factor; it is listed per model below where the architecture is published. Full formula and assumptions: methodology.
| Precision | Weight size | Required VRAM | Cheapest live fit | GPUs needed | Est. $/hr (full fit) |
|---|---|---|---|---|---|
| BF16 | 39.0 GB | 46.7 GB | RTX A6000 | 1 | $0.363/hr |
| cheaper alt. | RTX A5000 | 2 | $0.352/hr | ||
| FP8 (quantized) | 19.5 GB | 23.4 GB | RTX 4090 | 1 | $0.374/hr |
| INT4 (quantized) | 9.7 GB | 11.7 GB | RTX 3060 | 1 | $0.110/hr |
A GPU is only matched to a row if its hardware supports that precision, and the primary recommendation is always a single-GPU fit when one exists.
INT4 requires a quantized checkpoint actually published for this model, check its Hugging Face page before relying on this row.
Cheapest way to run gpt-oss-20b-BF16 at its published (BF16) precision: 1× RTX A6000, at $0.363/hr per GPU ($0.363/hr total). Quantizing to FP8 or INT4 (rows above) can cost less, but requires a compatible quantized checkpoint to exist for this model.
gpt-oss-20b-BF16: KV cache by context length
The KV cache is the memory the attention layers hold for every token of context, on top of the weights. It is not part of the flat 1.2x overhead in the table above, grows with context length and with every concurrent request, and is why a long-context deployment needs more VRAM than the table shows.
Sliding-window attention: windowed layers stop growing at the window, the full-attention layers keep growing. Cached per token: 49,152 bytes at 16-bit while the context is inside the window.
| Context | KV cache, one sequence |
|---|---|
| 4K | 0.10 GB |
| 32K | 0.75 GB |
| 128K | 3.0 GB |
Computed from the layer, head and window counts in the model's own configuration (unsloth/gpt-oss-20b-BF16), at 16 bits per cached value. Each concurrent sequence needs its own cache, on top of the weights.
gpt-oss-20b-BF16: common questions
Can gpt-oss-20b-BF16 run on a single GPU?
Yes, but not on a desktop card. At BF16 it needs 46.7 GB of VRAM, more than a single 32 GB desktop card holds. The cheapest live single-card fit is a 48.0 GB RTX A6000 at $0.363/hr.
What is the least VRAM gpt-oss-20b-BF16 can run in?
11.7 GB, at INT4 (quantized), which fits a 12 GB card, against 46.7 GB at BF16. That row assumes an INT4 checkpoint has actually been published for this model, so check its Hugging Face page before planning around it.
Does quantizing gpt-oss-20b-BF16 lower the GPU bill?
Yes. At BF16 the cheapest live fit is one RTX A6000 at $0.363/hr. At INT4 (quantized) it drops to one RTX 3060 at $0.110/hr, provided a quantized checkpoint exists for it.
Weight-to-VRAM math, the fit rules, and how live prices are normalized: full methodology.
More gpt-oss models
- Huihui-gpt-oss-20b-BF16-abliterated (20.9B, BF16)
- gpt-oss-20b (20.9B, MXFP4)
- gpt-oss-120b (116.8B, MXFP4)
- gpt-oss-120b-Eagle3-short-context (787M, BF16)
- EAGLE3-gpt-oss-20b (350M, BF16)
Lineage
Based on gpt-oss-20b.
Quantized and fine-tuned versions
Alternatives at this size
Other models for text-generation within about a third of gpt-oss-20b-BF16's 20.9B parameters, from other model lines.
- Qwen2.5-14B-Instruct (14.8B, BF16)
- GLM-4.7-Flash (31.2B, BF16)
- gpt-neox-20b (20.7B, F16)
- DeepSeek-Coder-V2-Lite-Instruct (15.7B, BF16)
- phi-4 (14.7B, BF16)
More on gpt-oss-20b-BF16
Fits on a 48 GB GPU at BF16: every model that fits in 48 GB.
Fits on a 24 GB GPU at FP8: every model that fits in 24 GB.
Fits on a 12 GB GPU at INT4: every model that fits in 12 GB.
Related reading: RTX A6000 pricing and specs, How much VRAM you need for LLMs, Serving LLMs with vLLM, vLLM vs TensorRT-LLM vs SGLang, Best GPU for LLM inference, and What AI model fine-tuning is.
