Grok 4 vs o3 Reasoning: which model should you choose?
We compared Grok 4 and o3 Reasoning on price, context window and 12 benchmarks. Grok 4 has the stronger average benchmark score; o3 Reasoning is cheaper on a blended 3:1 basis.
Grok 4
Grok 4 is a frontier model from xAI. It offers a 200,000-token context window, costs $17.90 per million input tokens and $84.75 per million output tokens, and averages 86.5 across the index's benchmark suite.
- Input
- $17.90 / 1M
- Output
- $84.75 / 1M
- Context
- 200,000
- Avg score
- 86.5
- Open weights
- No
o3 Reasoning
o3 Reasoning is a frontier model from OpenAI. It offers a 200,000-token context window, costs $18.07 per million input tokens and $70.65 per million output tokens, and averages 85.3 across the index's benchmark suite.
- Input
- $18.07 / 1M
- Output
- $70.65 / 1M
- Context
- 200,000
- Avg score
- 85.3
- Open weights
- No
Specification comparison
| Spec | Grok 4 | o3 Reasoning | Edge |
|---|---|---|---|
| Input price / 1M | $17.90 | $18.07 | A |
| Output price / 1M | $84.75 | $70.65 | B |
| Context window | 200,000 | 200,000 | Tie |
| Max output | 32,768 | 16,384 | A |
| Average score | 86.5 | 85.3 | A |
| Arena Elo | 1457.8 | 1456.9 | A |
| Open weights | No | No | Tie |
Benchmark comparison
Grok 4 wins 10, o3 Reasoning wins 2, and 0 benchmarks are tied. The table shows the modelled score for each model and the gap.
| Benchmark | Grok 4 | o3 Reasoning | Gap | Winner |
|---|---|---|---|---|
| MMLU-Pro | 87.8 | 87.7 | 0.1 | Grok 4 |
| GPQA Diamond | 82.6 | 79.6 | 3.0 | Grok 4 |
| SWE-bench Verified | 77.9 | 74.1 | 3.8 | Grok 4 |
| HumanEval | 92.0 | 91.3 | 0.7 | Grok 4 |
| MATH-500 | 90.8 | 92.0 | 1.2 | o3 Reasoning |
| AIME 2025 | 82.2 | 80.5 | 1.7 | Grok 4 |
| LiveCodeBench | 82.2 | 82.7 | 0.5 | o3 Reasoning |
| IFEval | 91.6 | 90.6 | 1.0 | Grok 4 |
| TruthfulQA | 87.6 | 86.5 | 1.1 | Grok 4 |
| HellaSwag | 93.9 | 90.9 | 3.0 | Grok 4 |
| MMMU | 82.9 | 82.3 | 0.6 | Grok 4 |
| Arena Elo | 1457.8 | 1456.9 | 0.9 | Grok 4 |
Price analysis
On a blended 3:1 input-to-output basis, Grok 4 costs about $34.61 per million tokens and o3 Reasoning costs about $31.22. o3 Reasoning is roughly 10% cheaper than Grok 4. At high volume, that gap compounds quickly, so price should carry real weight unless the quality difference is decisive.
Both models list a 200,000-token context window. That is enough for long documents, large codebases and multi-step agent traces.
Verdict
Across 12 shared benchmarks, Grok 4 wins 10, o3 Reasoning wins 2, and 0 are tied. On the index average, Grok 4 leads o3 Reasoning by 1.2 points (86.5 versus 85.3).
The price picture favours o3 Reasoning. The context picture is effectively a tie. Those two dimensions often matter more than a few benchmark points once a model is good enough for the task.
If you need a single default, start with Grok 4 for quality-sensitive work and o3 Reasoning for high-volume, well-scoped tasks. Run both on a sample of your own traffic before locking in a choice.
Choose Grok 4 if
- You want the higher average benchmark score in this index.
- You need the larger 32,768-token output limit.
Choose o3 Reasoning if
- Unit cost matters and you want the cheaper blended price.
FAQ
Is Grok 4 better than o3 Reasoning?
On the index average, Grok 4 leads o3 Reasoning by 1.2 points (86.5 versus 85.3). The better choice depends on price, context and your task. Grok 4 wins 10 benchmarks, o3 Reasoning wins 2.
Which is cheaper, Grok 4 or o3 Reasoning?
o3 Reasoning is cheaper on a blended 3:1 basis at about $31.22 per million tokens, versus $34.61 for Grok 4.
Which has the larger context window?
Both models list a 200,000-token context window.
Are these models open weights?
Grok 4 is proprietary; o3 Reasoning is proprietary.
Which should I choose for production?
If you need a single default, start with Grok 4 for quality-sensitive work and o3 Reasoning for high-volume, well-scoped tasks. Run both on a sample of your own traffic before locking in a choice.