o3 Reasoning vs o4: which model should you choose?
We compared o3 Reasoning and o4 on price, context window and 12 benchmarks. o4 has the stronger average benchmark score; o4 is cheaper on a blended 3:1 basis.
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
o4
o4 is a frontier model from OpenAI. It offers a 2,000,000-token context window, costs $17.74 per million input tokens and $66.00 per million output tokens, and averages 85.4 across the index's benchmark suite.
- Input
- $17.74 / 1M
- Output
- $66.00 / 1M
- Context
- 2,000,000
- Avg score
- 85.4
- Open weights
- No
Specification comparison
| Spec | o3 Reasoning | o4 | Edge |
|---|---|---|---|
| Input price / 1M | $18.07 | $17.74 | B |
| Output price / 1M | $70.65 | $66.00 | B |
| Context window | 200,000 | 2,000,000 | B |
| Max output | 16,384 | 8,192 | A |
| Average score | 85.3 | 85.4 | B |
| Arena Elo | 1456.9 | 1469.4 | B |
| Open weights | No | No | Tie |
Benchmark comparison
o3 Reasoning wins 6, o4 wins 6, and 0 benchmarks are tied. The table shows the modelled score for each model and the gap.
| Benchmark | o3 Reasoning | o4 | Gap | Winner |
|---|---|---|---|---|
| MMLU-Pro | 87.7 | 85.3 | 2.4 | o3 Reasoning |
| GPQA Diamond | 79.6 | 82.3 | 2.7 | o4 |
| SWE-bench Verified | 74.1 | 74.8 | 0.7 | o4 |
| HumanEval | 91.3 | 89.6 | 1.7 | o3 Reasoning |
| MATH-500 | 92.0 | 90.5 | 1.5 | o3 Reasoning |
| AIME 2025 | 80.5 | 85.3 | 4.8 | o4 |
| LiveCodeBench | 82.7 | 81.4 | 1.3 | o3 Reasoning |
| IFEval | 90.6 | 92.8 | 2.2 | o4 |
| TruthfulQA | 86.5 | 85.0 | 1.5 | o3 Reasoning |
| HellaSwag | 90.9 | 91.0 | 0.1 | o4 |
| MMMU | 82.3 | 80.9 | 1.4 | o3 Reasoning |
| Arena Elo | 1456.9 | 1469.4 | 12.5 | o4 |
Price analysis
On a blended 3:1 input-to-output basis, o3 Reasoning costs about $31.22 per million tokens and o4 costs about $29.80. o4 is roughly 5% cheaper than o3 Reasoning. At high volume, that gap compounds quickly, so price should carry real weight unless the quality difference is decisive.
o4 has the larger context window at 2,000,000 tokens, compared with 200,000 for o3 Reasoning. That matters for long documents, large codebases and multi-step agent traces.
Verdict
Across 12 shared benchmarks, o3 Reasoning wins 6, o4 wins 6, and 0 are tied. On the index average, o4 leads o3 Reasoning by 0.1 points (85.4 versus 85.3).
The price picture favours o4. The context picture favours o4. 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 o4 for quality-sensitive work, and check whether its price holds at your expected volume before committing.
Choose o3 Reasoning if
- You need the larger 16,384-token output limit.
Choose o4 if
- You want the higher average benchmark score in this index.
- Unit cost matters and you want the cheaper blended price.
- You need the larger 2,000,000-token context window.
FAQ
Is o3 Reasoning better than o4?
On the index average, o4 leads o3 Reasoning by 0.1 points (85.4 versus 85.3). The better choice depends on price, context and your task. o3 Reasoning wins 6 benchmarks, o4 wins 6.
Which is cheaper, o3 Reasoning or o4?
o4 is cheaper on a blended 3:1 basis at about $29.80 per million tokens, versus $31.22 for o3 Reasoning.
Which has the larger context window?
o4 has the larger context window at 2,000,000 tokens. o3 Reasoning has 200,000 tokens.
Are these models open weights?
o3 Reasoning is proprietary; o4 is proprietary.
Which should I choose for production?
If you need a single default, start with o4 for quality-sensitive work, and check whether its price holds at your expected volume before committing.