GPT-5.3 Codex vs Grok 4.5
Too close to call on our weighted score (GPT-5.3 Codex 64, Grok 4.5 64). The right pick depends on what you value most.
OpenAIGPT-5.3 Codex
64/100- ECI156.8
- Price$1.75 / $14.00
- Context400K
xAIGrok 4.5
64/100- ECI154.0
- Price$2.00 / $6.00
- Context500K
Add a model
Make it a three-way comparison.
Too close to call
It is close. Our weighted score puts them within a point (GPT-5.3 Codex 64/100, Grok 4.5 64/100), so choose by what matters most for your work: GPT-5.3 Codex for raw capability, Grok 4.5 on price and Grok 4.5 for long inputs. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.
- CapabilityGPT-5.3 CodexCapabilities Index (ECI): GPT-5.3 Codex 156.8 · Grok 4.5 154.0
- Lowest priceGrok 4.5Grok 4.5 $3.00 · GPT-5.3 Codex $4.81 per 1M tokens (3:1 blend)
- Longest contextGrok 4.5Grok 4.5 500,000 · GPT-5.3 Codex 400,000 tokens
- Widest inputsGPT-5.3 CodexGPT-5.3 Codex: Text, Images, PDFs · Grok 4.5: Text, Images
- Self-hostingNo open weightsBoth are available only through APIs
| Measure | Weight | GPT-5.3 Codex | Grok 4.5 |
|---|---|---|---|
| CapabilityCapabilities Index (ECI) | 50% | 87 | 83 |
| Price | 25% | 18 | 27 |
| Inputs & features | 15% | 80 | 70 |
| Context window | 10% | 44 | 48 |
| Overall | 100% | 64/100 | 64/100 |
Every spec in one table
Highlighted cells lead their row. Dashes mean the data is not published.
| Specification | GPT-5.3 CodexOpenAI | Grok 4.5xAI |
|---|---|---|
| Capability | ||
| Capabilities Index (ECI) | 156.8 (best) | 154.0 |
| ECI rank | #18 of 148 (best) | #36 of 148 |
| GPQA DiamondGraduate-level science questions | — | 93.4% |
| FrontierMath Tiers 1–3Research-level mathematics | — | 57.2% |
| OTIS Mock AIME 2024–2025Competition mathematics | — | 97.8% |
| SWE-bench VerifiedFixing real GitHub issues | 74.8% | — |
| SimpleQA VerifiedShort factual questions | — | 48.3% |
| Price per million tokens | ||
| Input | $1.75 (best) | $2.00 |
| Output | $14.00 | $6.00 (best) |
| Cached input | $0.175 (best) | $0.30 |
| Blended (3:1) | $4.81 | $3.00 (best) |
| Long-context rate | Same rate | Over 200K: $4.00 / $12.00 |
| Price source | Official OpenAI API | Official xAI API |
| Limits | ||
| Context window | 400,000 tokens | 500,000 tokens (best) |
| Max output | 128,000 tokens | 500,000 tokens (best) |
| Inputs and features | ||
| Text | Yes | Yes |
| Images | Yes | Yes |
| PDFs | Yes | No |
| Audio | No | No |
| Video | No | No |
| Reasoning | Yeslow · medium · high · xhigh | Yeslow · medium · high |
| Tool calling | Yes | Yes |
| Structured output | Yes | Yes |
| Availability | ||
| Weights | Proprietary | Proprietary |
| API model ID | gpt-5.3-codex | grok-4.5 |
| API providers | 19 | 24 (best) |
| Released | Feb 5, 2026 | Jul 8, 2026 |
| Knowledge cutoff | Aug 31, 2025 | — |
What would a month cost?
Enter your expected volume in millions of tokens. List prices only; caching and batch discounts would lower these.
- GPT-5.3 Codex$45.50
- Grok 4.5$32.00
Which should you choose?
Which is better: GPT-5.3 Codex or Grok 4.5?
It is close. Our weighted score puts them within a point (GPT-5.3 Codex 64/100, Grok 4.5 64/100), so choose by what matters most for your work: GPT-5.3 Codex for raw capability, Grok 4.5 on price and Grok 4.5 for long inputs. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.
Which is cheaper, GPT-5.3 Codex or Grok 4.5?
Grok 4.5 is cheaper at $2.00 input / $6.00 output per million tokens (official xAI API price). GPT-5.3 Codex costs $1.75 input / $14.00 output per million tokens (official OpenAI API price). At a typical mix of three input tokens to one output token, that is $3.00 per million tokens for Grok 4.5 versus $4.81 for GPT-5.3 Codex (1.6× as much).
Which scores higher on benchmarks?
GPT-5.3 Codex scores higher on the Capabilities Index (ECI): GPT-5.3 Codex 156.8 (#18 of 148) and Grok 4.5 154.0 (#36 of 148). The confidence ranges of the top two overlap (153.5–160.8 vs 152.3–156.1), so treat the gap as small.
Which is better for coding?
There are no published SWE-bench Verified results for Grok 4.5 yet, so there is no like-for-like coding score. On overall capability, GPT-5.3 Codex leads, which tends to carry over to coding, but test on your own codebase. Both support tool calling for agent workflows.
Which has the bigger context window?
Grok 4.5 has the largest context window at 500,000 tokens, against 400,000 for GPT-5.3 Codex. Maximum output per response: GPT-5.3 Codex up to 128,000, Grok 4.5 up to 500,000 tokens.
Which can read images, PDFs, audio or video?
GPT-5.3 Codex accepts text, images and PDFs; Grok 4.5 accepts text and images. GPT-5.3 Codex handles the widest range of inputs.
Are any of these open source?
No. GPT-5.3 Codex and Grok 4.5 are proprietary and only available through APIs and apps.
Which is newer?
Grok 4.5 is the newest, released Jul 8, 2026. GPT-5.3 Codex came out Feb 5, 2026. Knowledge cutoff: GPT-5.3 Codex Aug 31, 2025.
How do you decide the winner?
Each model gets a 0–100 score on capability (50%, independent benchmark results); price (25%, blended price per million tokens (3 input : 1 output), log scale); inputs & features (15%, image, PDF, audio and video input, tool calling, structured output and reasoning); context window (10%, maximum tokens per request, log scale). Dimensions missing for any model are dropped and the remaining weights rescaled, so every model is judged on the same evidence. Specs and prices come from public model listings and the labs’ own API pages; capability scores come from independent benchmark runs. Data updated Oct 4, 2026.
Related comparisons
- Add Gemini 3.1 Pro PreviewThree-way comparison
- GPT-5.3 Codex vs Gemini 3.1 Pro PreviewGoogle · ECI 154.8
- GPT-5.3 Codex vs Claude Sonnet 5Anthropic · ECI 156.3
- GPT-5.3 Codex vs Kimi K3Moonshot AI · ECI 157.6
- GPT-5.3 Codex vs Qwen3.8 MaxAlibaba (Qwen) · ECI 156.6
- Grok 4.5 vs Gemini 3.5 FlashGoogle · ECI 154.5
- Grok 4.5 vs Qwen3.8 Max 0902Alibaba (Qwen) · ECI 155.2
