o3 vs GPT-5-Codex
Too close to call on our weighted score (o3 42, GPT-5-Codex 42). The right pick depends on what you value most.
OpenAIo3
42/100- ECI146.9
- Price$2.00 / $8.00
- Context200K
- OpenAI
GPT-5-Codex
42/100- ECI—
- Price$1.25 / $10.00
- Context400K
Add a model
Make it a three-way comparison.
Too close to call
It is close. Our weighted score puts them within a point (o3 42/100, GPT-5-Codex 42/100), so choose by what matters most for your work: GPT-5-Codex on price and GPT-5-Codex for long inputs. The score weighs price 50%, inputs & features 30%, context window 20%. None of the shared benchmarks cover every model here yet, so capability is left out of this verdict.
- CapabilityNot enough dataNo independent benchmark covers every model here yet
- Lowest priceGPT-5-CodexGPT-5-Codex $3.44 · o3 $3.50 per 1M tokens (3:1 blend)
- Longest contextGPT-5-CodexGPT-5-Codex 400,000 · o3 200,000 tokens
- Widest inputso3o3: Text, Images, PDFs · GPT-5-Codex: Text, Images
- Self-hostingNo open weightsBoth are available only through APIs
| Measure | Weight | o3 | GPT-5-Codex |
|---|---|---|---|
| Price | 50% | 24 | 24 |
| Inputs & features | 30% | 80 | 70 |
| Context window | 20% | 32 | 44 |
| Overall | 100% | 42/100 | 42/100 |
Left out because at least one model lacks the data: capability. The remaining weights were rescaled.
Every spec in one table
Highlighted cells lead their row. Dashes mean the data is not published.
| Specification | o3OpenAI | GPT-5-CodexOpenAI |
|---|---|---|
| Capability | ||
| Capabilities Index (ECI) | 146.9 | — |
| ECI rank | #63 of 148 | — |
| GPQA DiamondGraduate-level science questions | 81.8% | — |
| FrontierMath Tiers 1–3Research-level mathematics | 33.3% | — |
| OTIS Mock AIME 2024–2025Competition mathematics | 84.4% | — |
| SWE-bench VerifiedFixing real GitHub issues | 62.3% | — |
| SimpleQA VerifiedShort factual questions | 49.4% | — |
| Price per million tokens | ||
| Input | $2.00 | $1.25 (best) |
| Output | $8.00 (best) | $10.00 |
| Cached input | $0.50 | — |
| Blended (3:1) | $3.50 | $3.44 (best) |
| Long-context rate | Same rate | Same rate |
| Price source | Official OpenAI API | Median of 3 providers |
| Limits | ||
| Context window | 200,000 tokens | 400,000 tokens (best) |
| Max output | 100,000 tokens | 128,000 tokens (best) |
| Inputs and features | ||
| Text | Yes | Yes |
| Images | Yes | Yes |
| PDFs | Yes | No |
| Audio | No | No |
| Video | No | No |
| Reasoning | Yeslow · medium · high | Yes |
| Tool calling | Yes | Yes |
| Structured output | Yes | Yes |
| Availability | ||
| Weights | Proprietary | Proprietary |
| API model ID | o3 | — |
| API providers | 18 (best) | 3 |
| Released | Apr 16, 2025 | Sep 15, 2025 |
| Knowledge cutoff | May 2024 | Sep 30, 2024 |
What would a month cost?
Enter your expected volume in millions of tokens. List prices only; caching and batch discounts would lower these.
- o3$36.00
- GPT-5-Codex$32.50
Which should you choose?
Which is better: o3 or GPT-5-Codex?
It is close. Our weighted score puts them within a point (o3 42/100, GPT-5-Codex 42/100), so choose by what matters most for your work: GPT-5-Codex on price and GPT-5-Codex for long inputs. The score weighs price 50%, inputs & features 30%, context window 20%. None of the shared benchmarks cover every model here yet, so capability is left out of this verdict.
Which is cheaper, o3 or GPT-5-Codex?
GPT-5-Codex is cheaper at $1.25 input / $10.00 output per million tokens (median across 3 API providers). o3 costs $2.00 input / $8.00 output per million tokens (official OpenAI API price). At a typical mix of three input tokens to one output token, that is $3.44 per million tokens for GPT-5-Codex versus $3.50 for o3 (1× as much).
Which scores higher on benchmarks?
There is no independent benchmark that covers both models yet. o3 has an ECI of 146.9 and GPT-5-Codex has not been scored yet.
Which is better for coding?
There are no published SWE-bench Verified results for GPT-5-Codex yet, so there is no like-for-like coding score. Test both on a sample of your own tasks. Both support tool calling for agent workflows.
Which has the bigger context window?
GPT-5-Codex has the largest context window at 400,000 tokens, against 200,000 for o3. Maximum output per response: o3 up to 100,000, GPT-5-Codex up to 128,000 tokens.
Which can read images, PDFs, audio or video?
o3 accepts text, images and PDFs; GPT-5-Codex accepts text and images. o3 handles the widest range of inputs.
Are any of these open source?
No. o3 and GPT-5-Codex are proprietary and only available through APIs and apps.
Which is newer?
GPT-5-Codex is the newest, released Sep 15, 2025. o3 came out Apr 16, 2025. Knowledge cutoff: o3 May 2024, GPT-5-Codex Sep 30, 2024.
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.
