GPT-5.3 Codex vs Grok 4.5
GPT-5.3 Codex (OpenAI) and Grok 4.5 (xAI) compared on benchmarks, pricing, context window, and use-case rankings.
- GPT-5.3 Codex leads on overall intelligence (ECI 156 vs 154).
- GPT-5.3 Codex is cheaper on input tokens — $1.75 vs $2.00 per 1M.
- Grok 4.5 has a larger context window (500K vs 400K tokens).
- Grok 4.5 ranks higher for coding (91th vs 67th percentile).
| Attribute | GPT-5.3 Codex | Grok 4.5 |
|---|---|---|
| Scores | ||
| Intelligence (ECI) | 156 | 154 |
| Coding | 67 | 91 |
| Math | — | 85 |
| Reasoning & Knowledge | 87 | 70 |
| Agentic & Tools | 67 | 75 |
| Specifications | ||
| Developer | OpenAI | xAI |
| Family | GPT | Grok |
| Released | Feb 5, 2026 | Jul 8, 2026 |
| Parameters | — | — |
| Availability | API access | API access |
| Context window | 400K | 500K |
| Price — $/M input | $1.75 | $2.00 |
| Price — $/M output | $14.00 | $6.00 |
| Inputs | text, image, file | text, image, file |
| Outputs | text | text |
| Benchmarks | ||
| APEX | 32% | 34% |
| GPQA Diamond | 92% | 93% |
| Humanity's Last Exam | 40% | 40% |
| METR task horizon | 5.8 h | — |
| SciCode | 53% | 54% |
| SWE-bench Verified | 75% | — |
| Terminal-Bench | 78% | — |
| WebDev Arena | 1407 | 1551 |
| WeirdML | 79% | 46% |
| τ²-bench | 86% | — |
| AIME 2024/2025 | — | 98% |
| ARC-AGI | — | 87% |
| ARC-AGI-2 | — | 53% |
| SimpleBench | — | 70% |
| SimpleQA Verified | — | 54% |
Use-case scores are 0–100 percentile composites across each area’s benchmarks, ranked against every model from the past year. Highlighted cells lead each row. Open a model for the full picture.
Frequently asked questions
Is GPT-5.3 Codex better than Grok 4.5?
On Epoch AI's Capabilities Index, GPT-5.3 Codex scores higher (156) than Grok 4.5 (154). The right pick depends on your task — compare their coding, math, and reasoning scores in the table above.
Which is cheaper, GPT-5.3 Codex or Grok 4.5?
GPT-5.3 Codex is cheaper on input tokens at $1.75 per million, versus $2.00 (representative OpenRouter pricing).
Which has a larger context window, GPT-5.3 Codex or Grok 4.5?
Grok 4.5 supports up to 500K tokens, compared with 400K for the other.
Which is better for coding, GPT-5.3 Codex or Grok 4.5?
Across coding benchmarks like SWE-bench Verified and Terminal-Bench, Grok 4.5 ranks higher — 91th vs 67th percentile among the models tracked on Model Beat.
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Benchmarks & model data from Epoch AI (CC BY); pricing & specs from OpenRouter. ECI = Epoch Capabilities Index.