API cost decision in 10 seconds

LFM2.5-1.2B-Thinking (free) vs GPT-5.1

Pick LFM2.5-1.2B-Thinking (free) for lower cost; pick GPT-5.1 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 LFM2.5-1.2B-Thinking (free) for lower cost; pick GPT-5.1 only if the larger context window matters more.

On the standard 1M input plus 500K output workload, LFM2.5-1.2B-Thinking (free) is estimated at $0 vs $6.25 for GPT-5.1, saving $6.25 (100% lower).

Cost-first pickLFM2.5-1.2B-Thinking (free)
Context-first pickGPT-5.1
Sample savings$6.25100%
10x traffic gap$62.5

GPT-5.1 has more context, but LFM2.5-1.2B-Thinking (free) 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.

LFM2.5-1.2B-Thinking (free) stays cheaper across input-heavy, balanced, and output-heavy sample workloads.

Workload shapeToken mixBetter pickLFM2.5-1.2B-Thinking (free)GPT-5.1
Input-heavy / RAG5M input + 500K outputLFM2.5-1.2B-Thinking (free)$0$11.25
Balanced workload1M input + 1M outputLFM2.5-1.2B-Thinking (free)$0$11.25
Output-heavy chatbot1M input + 5M outputLFM2.5-1.2B-Thinking (free)$0$51.25
Cheaper input LFM2.5-1.2B-Thinking (free) $0 vs $1.25 / 1M

LFM2.5-1.2B-Thinking (free) is free for input tokens while GPT-5.1 costs $1.25 per 1M tokens.

Cheaper output LFM2.5-1.2B-Thinking (free) $0 vs $10 / 1M

LFM2.5-1.2B-Thinking (free) is free for output tokens while GPT-5.1 costs $10 per 1M tokens.

Larger context GPT-5.1 32.77K vs 400K

GPT-5.1 has 367.23K more context (12.2x larger).

Sample workload LFM2.5-1.2B-Thinking (free) $0 vs $6.25

LFM2.5-1.2B-Thinking (free) 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.
LFM2.5-1.2B-Thinking (free) Calculating… Estimated API cost
GPT-5.1 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

LFM2.5-1.2B-Thinking (free) has the lower input price; LFM2.5-1.2B-Thinking (free) has the lower output price; GPT-5.1 offers the larger context window. For the 1M input plus 500K output sample, LFM2.5-1.2B-Thinking (free) is cheaper for the standard workload.

For a 1M input token plus 500K output token workload, the estimated API cost is $0 for LFM2.5-1.2B-Thinking (free) and $6.25 for GPT-5.1.

Best Fit

Choose LFM2.5-1.2B-Thinking (free) when you care most about lower input-token price, and lower output-token price.

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

Decision Notes
  • On the standard 1M input plus 500K output workload, LFM2.5-1.2B-Thinking (free) is estimated at $0 vs $6.25 for GPT-5.1, saving $6.25 (100% lower).
  • LFM2.5-1.2B-Thinking (free) is free for the standard workload while the other model is estimated at $6.25.
  • LFM2.5-1.2B-Thinking (free) is free for input tokens while GPT-5.1 costs $1.25 per 1M tokens.
  • LFM2.5-1.2B-Thinking (free) is free for output tokens while GPT-5.1 costs $10 per 1M tokens.
  • GPT-5.1 has 367.23K more context (12.2x larger).
Head-to-Head Specs
FeatureLFM2.5-1.2B-Thinking (free)
(LiquidAI)		GPT-5.1
(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 Window32.77K400K
Release Date

Use-Case Decision Matrix

Use caseBetter pickWhy
Budget-constrained productionLFM2.5-1.2B-Thinking (free)On the standard 1M input plus 500K output workload, LFM2.5-1.2B-Thinking (free) is estimated at $0 vs $6.25 for GPT-5.1, saving $6.25 (100% lower).
High-volume input processingLFM2.5-1.2B-Thinking (free)Lower prompt-token price matters most when prompts, retrieved passages, or documents dominate the bill.
Long responses and chatbotsLFM2.5-1.2B-Thinking (free)Lower output-token price matters most when assistants generate many completion tokens.
RAG or long-document workGPT-5.1A 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 when lower sample workload cost matters most: $0.
  • gpt-oss-20b (free) can replace GPT-5.1 when lower sample workload cost matters most: $0.
  • gpt-oss-20b can replace GPT-5.1 when lower sample workload cost matters most: $0.1.
  • gpt-oss-120b can replace GPT-5.1 when lower sample workload cost matters most: $0.13.
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Cheaper alternatives

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Larger context alternatives

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Provider catalogs

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LiquidAI catalog

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OpenAI catalog

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LFM2.5-1.2B-Thinking (free)

LFM2.5-1.2B-Thinking is a lightweight reasoning-focused model optimized for agentic tasks, data extraction, and RAG—while still running comfortably on edge devices. It supports long context (up to 32K tokens) and is...

GPT-5.1

GPT-5.1 is the latest frontier-grade model in the GPT-5 series, offering stronger general-purpose reasoning, improved instruction adherence, and a more natural conversational style compared to GPT-5. It uses adaptive reasoning...