High-volume, cost-sensitive work
Choose Gemini 3.1 Pro
Gemini 3.1 Pro costs 6% less on a typical mix of three input tokens for every output token ($4.50 against $4.81 per million tokens).
Gemini 3.1 Pro vs GPT-5.3-Codex: price, context and capabilities
Choose Gemini 3.1 Pro for high-volume, cost-sensitive work, writing and code generation, very long inputs and tool use and support agents. Choose GPT-5.3-Codex for reused prompts and documents (RAG, agents).
In short
- Gemini 3.1 Pro is 6% cheaper than GPT-5.3-Codex at the headline price ($4.50 / 1M tokens vs $4.81 / 1M tokens).
- Gemini 3.1 Pro reads more per request: 1.05M tokens against 400k.
Which should you choose?
Each answer below comes straight from the published prices, specifications and independent benchmark results.
Writing and code generation
Choose Gemini 3.1 Pro
Gemini 3.1 Pro charges $12.00 per million output tokens, against $14.00 for GPT-5.3-Codex. Output dominates the bill when answers are long.
Reused prompts and documents (RAG, agents)
Choose GPT-5.3-Codex
GPT-5.3-Codex charges $0.18 per million cached input tokens, against $0.20 for Gemini 3.1 Pro.
Very long inputs
Choose Gemini 3.1 Pro
Gemini 3.1 Pro reads up to 1.05M tokens per request, against 400k for GPT-5.3-Codex.
Agentic coding
Either one
They are practically level on Terminal-Bench Hard (53.8% and 53%).
Tool use and support agents
Choose Gemini 3.1 Pro
Gemini 3.1 Pro scores 95.6% on τ²-Bench (agentic tool use), against 86% for GPT-5.3-Codex.
Reasoning over long documents
Either one
They are practically level on Long-context reasoning (AA-LCR) (82% and 83.3%).
Monthly cost at three volumes
| Volume | Gemini 3.1 Pro | GPT-5.3-Codex | Difference |
|---|---|---|---|
| Prototype: 1M input, 250K output tokens | $5.00 | $5.25 | Gemini 3.1 Pro, $0.25 less |
| Production: 20M input, 5M output tokens | $100.00 | $105.00 | Gemini 3.1 Pro, $5.00 less |
| Scale: 500M input, 100M output tokens | $2,200 | $2,275 | Gemini 3.1 Pro, $75.00 less |
Standard rates, without caching or batch discounts. Volumes are per month.
Specifications side by side
| Gemini 3.1 Pro | GPT-5.3-Codex | |
|---|---|---|
| Provider | OpenAI | |
| Category | Language models | Language models |
| Status | Preview | Deprecated |
| Headline price | $4.50 / 1M tokens | $4.81 / 1M tokens |
| Input | $2.00 / 1M tokens | $1.75 / 1M tokens |
| Output | $12.00 / 1M tokens | $14.00 / 1M tokens |
| Cached input | $0.20 / 1M tokens | $0.175 / 1M tokens |
| Context window | 1.05M | 400k |
| Max output | 66k | 128k |
| Released | February 2026 | Feb 24, 2026 |
| Knowledge cutoff | No data | August 2025 |
| Licence | Proprietary | Proprietary |
| Capabilities | Vision, Reasoning, Tool calling, Structured output, Prompt caching, Batch API | Vision, Reasoning, Tool calling, Structured output, Prompt caching, Batch API |
| API model id | gemini-3.1-pro-preview | gpt-5.3-codex |
Benchmarks side by side
Leader in bold.
| Benchmark | Gemini 3.1 Pro | GPT-5.3-Codex |
|---|---|---|
| Terminal-Bench Hard | 53.8% | 53% |
| GPQA Diamond | 94.1% | 91.5% |
| Humanity's Last Exam | 47% | 42.5% |
| IFBench (instruction following) | 77.1% | 75.4% |
| τ²-Bench (agentic tool use) | 95.6% | 86% |
| MMMU-Pro (visual reasoning) | 82.4% | 78.5% |
| Long-context reasoning (AA-LCR) | 82% | 83.3% |
| Intelligence Index | 29.7 | No data |
| SciCode | 58.7% | No data |
Independent evaluations by Artificial Analysis, run the same way for every model, at the reasoning setting shown. Percentages unless marked as an index.
Frequently asked questions
Should I choose Gemini 3.1 Pro or GPT-5.3-Codex?
Choose Gemini 3.1 Pro for high-volume, cost-sensitive work, writing and code generation, very long inputs and tool use and support agents. Choose GPT-5.3-Codex for reused prompts and documents (RAG, agents).
Which is cheaper, Gemini 3.1 Pro or GPT-5.3-Codex?
Gemini 3.1 Pro is 6% cheaper than GPT-5.3-Codex at the headline price ($4.50 / 1M tokens vs $4.81 / 1M tokens).
Which has the larger context window, Gemini 3.1 Pro or GPT-5.3-Codex?
Gemini 3.1 Pro reads more per request: 1.05M tokens against 400k.
What is the difference between Gemini 3.1 Pro and GPT-5.3-Codex?
Gemini 3.1 Pro is made by Google and GPT-5.3-Codex by OpenAI. Gemini 3.1 Pro is 6% cheaper than GPT-5.3-Codex at the headline price ($4.50 / 1M tokens vs $4.81 / 1M tokens). Gemini 3.1 Pro reads more per request: 1.05M tokens against 400k.
Which is better for coding, Gemini 3.1 Pro or GPT-5.3-Codex?
They are practically level on Terminal-Bench Hard (53.8% and 53%).
How much do Gemini 3.1 Pro and GPT-5.3-Codex cost per month?
At 20 million input and 5 million output tokens a month, Gemini 3.1 Pro costs $100.00 and GPT-5.3-Codex costs $105.00, at standard rates.