Claude Sonnet 4.5 vs Grok 4: which model should you choose?
We compared Claude Sonnet 4.5 and Grok 4 on price, context window and 12 benchmarks. Grok 4 has the stronger average benchmark score; Claude Sonnet 4.5 is cheaper on a blended 3:1 basis.
Claude Sonnet 4.5
Claude Sonnet 4.5 is a frontier model from Anthropic. It offers a 400,000-token context window, costs $17.84 per million input tokens and $70.50 per million output tokens, and averages 86.0 across the index's benchmark suite.
- Input
- $17.84 / 1M
- Output
- $70.50 / 1M
- Context
- 400,000
- Avg score
- 86.0
- Open weights
- No
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
Specification comparison
| Spec | Claude Sonnet 4.5 | Grok 4 | Edge |
|---|---|---|---|
| Input price / 1M | $17.84 | $17.90 | A |
| Output price / 1M | $70.50 | $84.75 | A |
| Context window | 400,000 | 200,000 | A |
| Max output | 128,000 | 32,768 | A |
| Average score | 86.0 | 86.5 | B |
| Arena Elo | 1478.2 | 1457.8 | A |
| Open weights | No | No | Tie |
Benchmark comparison
Claude Sonnet 4.5 wins 5, Grok 4 wins 6, and 1 benchmarks are tied. The table shows the modelled score for each model and the gap.
| Benchmark | Claude Sonnet 4.5 | Grok 4 | Gap | Winner |
|---|---|---|---|---|
| MMLU-Pro | 88.0 | 87.8 | 0.2 | Claude Sonnet 4.5 |
| GPQA Diamond | 82.6 | 82.6 | 0.0 | Tie |
| SWE-bench Verified | 74.2 | 77.9 | 3.7 | Grok 4 |
| HumanEval | 92.7 | 92.0 | 0.7 | Claude Sonnet 4.5 |
| MATH-500 | 87.0 | 90.8 | 3.8 | Grok 4 |
| AIME 2025 | 86.3 | 82.2 | 4.1 | Claude Sonnet 4.5 |
| LiveCodeBench | 82.5 | 82.2 | 0.3 | Claude Sonnet 4.5 |
| IFEval | 91.1 | 91.6 | 0.5 | Grok 4 |
| TruthfulQA | 87.2 | 87.6 | 0.4 | Grok 4 |
| HellaSwag | 93.0 | 93.9 | 0.9 | Grok 4 |
| MMMU | 80.9 | 82.9 | 2.0 | Grok 4 |
| Arena Elo | 1478.2 | 1457.8 | 20.4 | Claude Sonnet 4.5 |
Price analysis
On a blended 3:1 input-to-output basis, Claude Sonnet 4.5 costs about $31.00 per million tokens and Grok 4 costs about $34.61. Claude Sonnet 4.5 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.
Claude Sonnet 4.5 has the larger context window at 400,000 tokens, compared with 200,000 for Grok 4. That matters for long documents, large codebases and multi-step agent traces.
Verdict
Across 12 shared benchmarks, Claude Sonnet 4.5 wins 5, Grok 4 wins 6, and 1 are tied. On the index average, Grok 4 leads Claude Sonnet 4.5 by 0.5 points (86.5 versus 86.0).
The price picture favours Claude Sonnet 4.5. The context picture favours Claude Sonnet 4.5. 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 Claude Sonnet 4.5 for high-volume, well-scoped tasks. Run both on a sample of your own traffic before locking in a choice.
Choose Claude Sonnet 4.5 if
- Unit cost matters and you want the cheaper blended price.
- You need the larger 400,000-token context window.
- You need the larger 128,000-token output limit.
Choose Grok 4 if
- You want the higher average benchmark score in this index.
FAQ
Is Claude Sonnet 4.5 better than Grok 4?
On the index average, Grok 4 leads Claude Sonnet 4.5 by 0.5 points (86.5 versus 86.0). The better choice depends on price, context and your task. Claude Sonnet 4.5 wins 5 benchmarks, Grok 4 wins 6.
Which is cheaper, Claude Sonnet 4.5 or Grok 4?
Claude Sonnet 4.5 is cheaper on a blended 3:1 basis at about $31.00 per million tokens, versus $34.61 for Grok 4.
Which has the larger context window?
Claude Sonnet 4.5 has the larger context window at 400,000 tokens. Grok 4 has 200,000 tokens.
Are these models open weights?
Claude Sonnet 4.5 is proprietary; Grok 4 is proprietary.
Which should I choose for production?
If you need a single default, start with Grok 4 for quality-sensitive work and Claude Sonnet 4.5 for high-volume, well-scoped tasks. Run both on a sample of your own traffic before locking in a choice.