API cost decision in 10 seconds

Free Models Router vs GPT-5.1-Codex-Max

Pick Free Models Router for lower cost; pick GPT-5.1-Codex-Max only if the larger context window matters more.

Page updated:  Data confirmed:  Prices normalized to USD per 1M tokens Sample workload: 1M input + 500K output

Budget verdict

Pick Free Models Router for lower cost; pick GPT-5.1-Codex-Max only if the larger context window matters more.

On the standard 1M input plus 500K output workload, Free Models Router is estimated at $0 vs $6.25 for GPT-5.1-Codex-Max, saving $6.25 (100% lower).

Cost-first pickFree Models Router
Context-first pickGPT-5.1-Codex-Max
Sample savings$6.25100%
10x traffic gap$62.5

GPT-5.1-Codex-Max has more context, but Free Models Router saves $6.25 on the standard workload. At 10x that traffic, the same price gap is about $62.5. Use the calculator below to replace the sample workload with your own token volume.

Cost sensitivity

Workload Sensitivity

Same prices, different token mixes.

Free Models Router stays cheaper across input-heavy, balanced, and output-heavy sample workloads.

Workload shapeToken mixBetter pickFree Models RouterGPT-5.1-Codex-Max
Input-heavy / RAG5M input + 500K outputFree Models Router$0$11.25
Balanced workload1M input + 1M outputFree Models Router$0$11.25
Output-heavy chatbot1M input + 5M outputFree Models Router$0$51.25
Cheaper input Free Models Router $0 vs $1.25 / 1M

Free Models Router is free for input tokens while GPT-5.1-Codex-Max costs $1.25 per 1M tokens.

Cheaper output Free Models Router $0 vs $10 / 1M

Free Models Router is free for output tokens while GPT-5.1-Codex-Max costs $10 per 1M tokens.

Larger context GPT-5.1-Codex-Max 200K vs 400K

GPT-5.1-Codex-Max has 200K more context (2x larger).

Sample workload Free Models Router $0 vs $6.25

Free Models Router is free for the standard workload while the other model is estimated at $6.25.

Estimate your workload cost

Your Workload Cost

Prices are normalized to USD per 1M tokens.
Free Models Router Calculating… Estimated API cost
GPT-5.1-Codex-Max Calculating… Estimated API cost
Cheaper for this workload Calculating… Difference: calculating…

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

Verdict

Free Models Router has the lower input price; Free Models Router has the lower output price; GPT-5.1-Codex-Max offers the larger context window. For the 1M input plus 500K output sample, Free Models Router is cheaper for the standard workload.

For a 1M input token plus 500K output token workload, the estimated API cost is $0 for Free Models Router and $6.25 for GPT-5.1-Codex-Max.

Best Fit

Choose Free Models Router when you care most about lower input-token price, and lower output-token price.

Choose GPT-5.1-Codex-Max when you care most about larger context window.

Decision Notes
  • On the standard 1M input plus 500K output workload, Free Models Router is estimated at $0 vs $6.25 for GPT-5.1-Codex-Max, saving $6.25 (100% lower).
  • Free Models Router is free for the standard workload while the other model is estimated at $6.25.
  • Free Models Router is free for input tokens while GPT-5.1-Codex-Max costs $1.25 per 1M tokens.
  • Free Models Router is free for output tokens while GPT-5.1-Codex-Max costs $10 per 1M tokens.
  • GPT-5.1-Codex-Max has 200K more context (2x larger).
Head-to-Head Specs
FeatureFree Models Router
(OpenRouter)		GPT-5.1-Codex-Max
(OpenAI)
Input Price
prompt tokens per 1M		$0$1.25
Completion Price
per 1M tokens		$0$10
Sample Workload Cost
1M input + 500K output		$0$6.25
Context Window200K400K
Release Date

Use-Case Decision Matrix

Use caseBetter pickWhy
Budget-constrained productionFree Models RouterOn the standard 1M input plus 500K output workload, Free Models Router is estimated at $0 vs $6.25 for GPT-5.1-Codex-Max, saving $6.25 (100% lower).
High-volume input processingFree Models RouterLower prompt-token price matters most when prompts, retrieved passages, or documents dominate the bill.
Long responses and chatbotsFree Models RouterLower output-token price matters most when assistants generate many completion tokens.
RAG or long-document workGPT-5.1-Codex-MaxA larger context window leaves more room for retrieved passages, conversation history, or source files.

Related Alternatives

Same-provider lower-cost swaps
  • gpt-oss-120b (free) can replace GPT-5.1-Codex-Max when lower sample workload cost matters most: $0.
  • gpt-oss-20b (free) can replace GPT-5.1-Codex-Max when lower sample workload cost matters most: $0.
  • gpt-oss-20b can replace GPT-5.1-Codex-Max when lower sample workload cost matters most: $0.1.
  • gpt-oss-120b can replace GPT-5.1-Codex-Max when lower sample workload cost matters most: $0.13.
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