comparison
Grok 4.20 vs gpt-oss-120b
Token pricing, context window and real monthly cost, side by side. gpt-oss-120b is the cheaper of the two for a typical workload — about 6.0× less.
Positioned by published specs — size, context and modality — not measured performance; a smaller model can sometimes outperform a larger one on your task.
Grok 4.20 is one class larger (Flagship vs Mid). Lean to the cheaper gpt-oss-120b unless your task is demanding enough to need the larger class.
| metric | Grok 4.20 | gpt-oss-120b |
|---|---|---|
| Input / 1M | $1.25 | $0.15 |
| Output / 1M | $2.50 | $0.60 |
| Context | 2M | 131K |
| Technical class | Flagship | Mid |
| Cost @ typical workload | $625/mo | $105/mo |
| Modality | text + image | Text only |
| Price source | list | routed |
| Provider | xAI | OpenAI |
Snapshot . Cost uses a typical workload; tune it in the calculator. How we measure →
Which should you pick?
On a typical workload, gpt-oss-120b costs $105/mo against Grok 4.20's $625/mo — roughly 6.0× cheaper. But the ranking depends on your output-to-input ratio: output is the pricier direction for both, so an output-heavy job (code generation, long answers) widens the gap while an input-heavy one (summarization, retrieval) narrows it. If you need to fit more in a single prompt, Grok 4.20 has the larger 2M-token window (~3,000 pages). Only Grok 4.20 accepts image input — decisive if your prompts include images. By technical class (size and context, not measured capability), Grok 4.20 is a Flagship and gpt-oss-120b a Mid — so the lower price partly reflects a smaller class, not just a discount.
These are list and routed market prices, not measured outcomes. Two models at the same rate can still cost different amounts to finish the same task, because verbose or reasoning-heavy models emit more tokens. That gap is exactly what measured cost-per-task captures. The technical-class read above is likewise spec-based — size, context and modality, not measured performance — so a smaller model can still outperform a larger one on your specific task.
Frequently asked questions
Is Grok 4.20 or gpt-oss-120b cheaper?
For a typical workload (1,500 input + 500 output tokens × 200,000 requests/month), gpt-oss-120b costs $105/mo versus $625/mo for Grok 4.20 — about 6.0× less. Because output is priced higher than input, the winner can flip if your workload writes much more or less than this; check your own numbers in the calculator.
What's the main difference between Grok 4.20 and gpt-oss-120b?
On price, Grok 4.20 is $1.25/$2.50 per 1M (in/out) and gpt-oss-120b is $0.15/$0.60. By technical class (size & context) it's Flagship (Grok 4.20) versus Mid (gpt-oss-120b). Grok 4.20 has the larger context window at 2M tokens. Only Grok 4.20 accepts image input.
Why is gpt-oss-120b so much cheaper than Grok 4.20?
gpt-oss-120b has a much lower per-token rate — $0.60/1M output versus $2.50, and it's a smaller technical class (Mid vs Flagship). The headline rate isn't the whole story, though: a verbose model can cost more to finish a task than its rate implies — that's what measured cost-per-task captures.
Which handles longer prompts, Grok 4.20 or gpt-oss-120b?
Grok 4.20 — its 2M-token context window (~3,000 pages of text) is the larger of the two, by roughly 15×.
More comparisons
- GPT-5.5 vs gpt-oss-120b
- GPT-5.4 vs gpt-oss-120b
- GPT-5.4 mini vs gpt-oss-120b
- GPT-5.4 mini vs Grok 4.20
- GPT-5.4 nano vs gpt-oss-120b
- Grok 4.20 vs GPT-5.4 nano
Related
- Grok 4.20 and gpt-oss-120b — full specs and price history.
- API cost calculator — compare on your own workload.
- All comparisons — the full head-to-head index.