GPT-OSS 20B vs o4
OpenAI's open-weights return. Meanwhile, o4: reasoning model. thinks before it speaks.
Side-by-side
Specs
| Dimension | GPT-OSS 20B | o4 |
|---|---|---|
| Provider | OpenAI | OpenAI |
| Released | 2025-09 | 2025-09 |
| Context window | 128K | ✓200K |
| Output max | 8K | ✓100K |
| Input /M | ✓$0.15 | $15.00 |
| Output /M | ✓$0.60 | $60.00 |
| Modalities | text | ✓text, image |
| Open weights | ✓yes | no |
Scorecard
Dimension-by-dimension
GPT-OSS 20B
o4
reasoning
7.0
10.0
coding
7.0
9.0
writing
7.0
7.0
speed
9.0
3.0
value
10.0
5.0
Verdict
Which wins, by use case
| Use case | Winner | Why |
|---|---|---|
| coding | o4 | a clear edge on our weighted coding score |
| writing | GPT-OSS 20B | a coin flip on our weighted writing score |
| chat | GPT-OSS 20B | a decisive lead on our weighted chat score |
| agents | o4 | a clear edge on our weighted agents score |
| summarization | GPT-OSS 20B | a decisive lead on our weighted summarization score |
| translation | GPT-OSS 20B | a decisive lead on our weighted translation score |
| reasoning | o4 | a decisive lead on our weighted reasoning score |
| research | GPT-OSS 20B | a coin flip on our weighted research score |
| vision and multimodal | o4 | a coin flip on our weighted vision score |
| Cheapest AI models for bulk workloads | GPT-OSS 20B | a decisive lead on our weighted cheap-bulk score |
Bottom line
Our take
Pick GPT-OSS 20B if you need: single-gpu inference, open weights.
Pick o4 if you need: state-of-the-art math & science, complex planning.
At a 500M-input / 150M-output monthly volume, GPT-OSS 20B costs roughly $165 vs o4 at $16500. Use our calculator to plug in your own numbers.
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