GPT-5.1-Codex is $0.75 cheaper per 1M input tokens (37.5% lower; 1.6x difference).
API cost decision in 10 seconds
Gemini 3.1 Pro Preview Custom Tools vs GPT-5.1-Codex
Pick GPT-5.1-Codex for lower cost; pick Gemini 3.1 Pro Preview Custom Tools only if the larger context window matters more.
Pricing data updated:
Prices normalized to USD per 1M tokens
Sample workload: 1M input + 500K output
Budget verdict
Pick GPT-5.1-Codex for lower cost; pick Gemini 3.1 Pro Preview Custom Tools only if the larger context window matters more.
On the standard 1M input plus 500K output workload, GPT-5.1-Codex is estimated at $6.25 vs $8 for Gemini 3.1 Pro Preview Custom Tools, saving $1.75 (21.9% lower).
Cost-first pickGPT-5.1-Codex
Context-first pickGemini 3.1 Pro Preview Custom Tools
Sample savings$1.7521.9%
10x traffic gap$17.5
Gemini 3.1 Pro Preview Custom Tools has more context, but GPT-5.1-Codex saves $1.75 on the standard workload. At 10x that traffic, the same price gap is about $17.5. Use the calculator below to replace the sample workload with your own token volume.
Cost sensitivity
Workload Sensitivity
GPT-5.1-Codex stays cheaper across input-heavy, balanced, and output-heavy sample workloads.
| Workload shape | Token mix | Better pick | Gemini 3.1 Pro Preview Custom Tools | GPT-5.1-Codex |
|---|---|---|---|---|
| Input-heavy / RAG | 5M input + 500K output | GPT-5.1-Codex | $16 | $11.25 |
| Balanced workload | 1M input + 1M output | GPT-5.1-Codex | $14 | $11.25 |
| Output-heavy chatbot | 1M input + 5M output | GPT-5.1-Codex | $62 | $51.25 |
GPT-5.1-Codex is $2 cheaper per 1M output tokens (16.7% lower; 1.2x difference).
Gemini 3.1 Pro Preview Custom Tools has 648.76K more context (2.62x larger).
GPT-5.1-Codex is $1.75 cheaper on the standard workload (21.9% lower).
Estimate your workload cost
Your Workload Cost
This estimate uses normalized public API pricing per 1M tokens. It is a planning aid, not a billing quote. Verify provider pricing, limits, and terms before production use.
Quick Decision
GPT-5.1-Codex has the lower input price; GPT-5.1-Codex has the lower output price; Gemini 3.1 Pro Preview Custom Tools offers the larger context window. For the 1M input plus 500K output sample, GPT-5.1-Codex is cheaper for the standard workload.
For a 1M input token plus 500K output token workload, the estimated API cost is $8 for Gemini 3.1 Pro Preview Custom Tools and $6.25 for GPT-5.1-Codex.
Choose Gemini 3.1 Pro Preview Custom Tools when you care most about larger context window.
Choose GPT-5.1-Codex when you care most about lower input-token price, and lower output-token price.
- On the standard 1M input plus 500K output workload, GPT-5.1-Codex is estimated at $6.25 vs $8 for Gemini 3.1 Pro Preview Custom Tools, saving $1.75 (21.9% lower).
- GPT-5.1-Codex is $1.75 cheaper on the standard workload (21.9% lower).
- GPT-5.1-Codex is $0.75 cheaper per 1M input tokens (37.5% lower; 1.6x difference).
- GPT-5.1-Codex is $2 cheaper per 1M output tokens (16.7% lower; 1.2x difference).
- Gemini 3.1 Pro Preview Custom Tools has 648.76K more context (2.62x larger).
| Feature | Gemini 3.1 Pro Preview Custom Tools (Google) | GPT-5.1-Codex (OpenAI) |
|---|---|---|
| Input Price prompt tokens per 1M | $2 | $1.25 |
| Completion Price per 1M tokens | $12 | $10 |
| Sample Workload Cost 1M input + 500K output | $8 | $6.25 |
| Context Window | 1.05M | 400K |
| Release Date |
Use-Case Decision Matrix
| Use case | Better pick | Why |
|---|---|---|
| Budget-constrained production | GPT-5.1-Codex | On the standard 1M input plus 500K output workload, GPT-5.1-Codex is estimated at $6.25 vs $8 for Gemini 3.1 Pro Preview Custom Tools, saving $1.75 (21.9% lower). |
| High-volume input processing | GPT-5.1-Codex | Lower prompt-token price matters most when prompts, retrieved passages, or documents dominate the bill. |
| Long responses and chatbots | GPT-5.1-Codex | Lower output-token price matters most when assistants generate many completion tokens. |
| RAG or long-document work | Gemini 3.1 Pro Preview Custom Tools | A larger context window leaves more room for retrieved passages, conversation history, or source files. |
Related Alternatives
- Gemma 4 26B A4B (free) can replace Gemini 3.1 Pro Preview Custom Tools when lower sample workload cost matters most: $0.
- Gemma 4 31B (free) can replace Gemini 3.1 Pro Preview Custom Tools when lower sample workload cost matters most: $0.
- Lyria 3 Pro Preview can replace Gemini 3.1 Pro Preview Custom Tools when lower sample workload cost matters most: $0.
- Lyria 3 Clip Preview can replace Gemini 3.1 Pro Preview Custom Tools when lower sample workload cost matters most: $0.
- Llama 4 Scout offers 10M context with $0.23 sample workload cost.
- Grok 4.20 Multi-Agent offers 2M context with $5 sample workload cost.
- Grok 4.20 offers 2M context with $2.5 sample workload cost.
- GPT-5.4 offers 1.05M context with $10 sample workload cost.
- No popular competitor is currently available.
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