Rnj 1 Instruct is $1.1 cheaper per 1M input tokens (88% lower; 8.33x difference).
API cost decision in 10 seconds
Rnj 1 Instruct vs GPT-5.1-Codex
Pick Rnj 1 Instruct for lower cost; pick GPT-5.1-Codex 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 Rnj 1 Instruct for lower cost; pick GPT-5.1-Codex only if the larger context window matters more.
On the standard 1M input plus 500K output workload, Rnj 1 Instruct is estimated at $0.22 vs $6.25 for GPT-5.1-Codex, saving $6.03 (96.4% lower).
Cost-first pickRnj 1 Instruct
Context-first pickGPT-5.1-Codex
Sample savings$6.0396.4%
10x traffic gap$60.25
GPT-5.1-Codex has more context, but Rnj 1 Instruct saves $6.03 on the standard workload. At 10x that traffic, the same price gap is about $60.25. Use the calculator below to replace the sample workload with your own token volume.
Cost sensitivity
Workload Sensitivity
Rnj 1 Instruct stays cheaper across input-heavy, balanced, and output-heavy sample workloads.
| Workload shape | Token mix | Better pick | Rnj 1 Instruct | GPT-5.1-Codex |
|---|---|---|---|---|
| Input-heavy / RAG | 5M input + 500K output | Rnj 1 Instruct | $0.82 | $11.25 |
| Balanced workload | 1M input + 1M output | Rnj 1 Instruct | $0.3 | $11.25 |
| Output-heavy chatbot | 1M input + 5M output | Rnj 1 Instruct | $0.9 | $51.25 |
Rnj 1 Instruct is $9.85 cheaper per 1M output tokens (98.5% lower; 66.7x difference).
GPT-5.1-Codex has 367.23K more context (12.2x larger).
Rnj 1 Instruct is $6.03 cheaper on the standard workload (96.4% 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
Rnj 1 Instruct has the lower input price; Rnj 1 Instruct has the lower output price; GPT-5.1-Codex offers the larger context window. For the 1M input plus 500K output sample, Rnj 1 Instruct is cheaper for the standard workload.
For a 1M input token plus 500K output token workload, the estimated API cost is $0.22 for Rnj 1 Instruct and $6.25 for GPT-5.1-Codex.
Choose Rnj 1 Instruct when you care most about lower input-token price, and lower output-token price.
Choose GPT-5.1-Codex when you care most about larger context window.
- On the standard 1M input plus 500K output workload, Rnj 1 Instruct is estimated at $0.22 vs $6.25 for GPT-5.1-Codex, saving $6.03 (96.4% lower).
- Rnj 1 Instruct is $6.03 cheaper on the standard workload (96.4% lower).
- Rnj 1 Instruct is $1.1 cheaper per 1M input tokens (88% lower; 8.33x difference).
- Rnj 1 Instruct is $9.85 cheaper per 1M output tokens (98.5% lower; 66.7x difference).
- GPT-5.1-Codex has 367.23K more context (12.2x larger).
| Feature | Rnj 1 Instruct (EssentialAI) | GPT-5.1-Codex (OpenAI) |
|---|---|---|
| Input Price prompt tokens per 1M | $0.15 | $1.25 |
| Completion Price per 1M tokens | $0.15 | $10 |
| Sample Workload Cost 1M input + 500K output | $0.22 | $6.25 |
| Context Window | 32.77K | 400K |
| Release Date |
Use-Case Decision Matrix
| Use case | Better pick | Why |
|---|---|---|
| Budget-constrained production | Rnj 1 Instruct | On the standard 1M input plus 500K output workload, Rnj 1 Instruct is estimated at $0.22 vs $6.25 for GPT-5.1-Codex, saving $6.03 (96.4% lower). |
| High-volume input processing | Rnj 1 Instruct | Lower prompt-token price matters most when prompts, retrieved passages, or documents dominate the bill. |
| Long responses and chatbots | Rnj 1 Instruct | Lower output-token price matters most when assistants generate many completion tokens. |
| RAG or long-document work | GPT-5.1-Codex | A larger context window leaves more room for retrieved passages, conversation history, or source files. |
Related Alternatives
- gpt-oss-120b (free) can replace GPT-5.1-Codex when lower sample workload cost matters most: $0.
- gpt-oss-20b (free) can replace GPT-5.1-Codex when lower sample workload cost matters most: $0.
- gpt-oss-20b can replace GPT-5.1-Codex when lower sample workload cost matters most: $0.1.
- gpt-oss-120b can replace GPT-5.1-Codex when lower sample workload cost matters most: $0.13.
- 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.
- Owl Alpha offers 1.05M context with $0 sample workload cost.
- No popular competitor is currently available.
Cheaper alternatives
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Open cheapest modelsLarger context alternatives
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Open OpenAI modelsRnj-1 is an 8B-parameter, dense, open-weight model family developed by Essential AI and trained from scratch with a focus on programming, math, and scientific reasoning. The model demonstrates strong performance...
GPT-5.1-Codex is a specialized version of GPT-5.1 optimized for software engineering and coding workflows. It is designed for both interactive development sessions and long, independent execution of complex engineering tasks....