AI comparison report

Gpt-4.1 vs Gpt-5.1

By CompareAI Editorial Team · Published 2026-10-10 · How we compare

Choose GPT-4.1 for an established 1M token context window, lower output token pricing, and lightweight Nano/Mini model tiers, or select GPT-5.1 for superior ad…

Who wins: Gpt-4.1 or Gpt-5.1?

Choose GPT-5.1 first if the workload demands complex adaptive reasoning, integrated web search, or high-volume prompt input processing at $1.25 per million tokens, but verify its actual context limits before deployment; otherwise, select GPT-4.1 if guaranteed 1M token context capacity, cheaper $8.00/1M output tokens, or lightweight Nano/Mini tiers are needed.

Based on our analysis across 5 dimensions with 16 sources, Gpt-4.1 scores 7.9/10 overall while Gpt-5.1 scores 8.3/10 overall.

DimensionGpt-4.1Gpt-5.1
Reasoning Architecture & Benchmark Performance7.2/109.4/10
Context Window & Output Limits8.5/106.5/10
Model Family Variants & Personalization8/108.5/10
API Pricing & Cost Efficiency7.5/107.5/10
Developer Tooling & Multimodal Support8.2/109.4/10
Overall7.9/108.3/10

Should I choose Gpt-4.1 or Gpt-5.1?

Verdict: Choose GPT-5.1 first if the workload demands complex adaptive reasoning, integrated web search, or high-volume prompt input processing at $1.25 per million tokens, but verify its actual context limits before deployment; otherwise, select GPT-4.1 if guaranteed 1M token context capacity, cheaper $8.00/1M output tokens, or lightweight Nano/Mini tiers are needed.

Choose GPT-4.1 for an established 1M token context window, lower output token pricing, and lightweight Nano/Mini model tiers, or select GPT-5.1 for superior adaptive reasoning performance and integrated web search.

GPT-5.1 leads in complex reasoning and input-heavy economics, achieving 94.0% on AIME 2025, 87.3% on GPQA Diamond, and 86.8% on LiveCodeBench with dynamic adaptive reasoning modes (Instant and Thinking) and a cheaper input cost of $1.25 per million tokens compared to GPT-4.1's $2.00 per million tokens. Conversely, GPT-4.1 is preferable for massive context and output-heavy pipelines, providing an established 1M token input context window via API (with up to 33K output tokens), a 21.4% improvement on SWE-bench Verified operating up to 40% faster than GPT-4o/GPT-4.5, cheaper output pricing at $8.00 per million tokens (versus $10.00 for GPT-5.1), and smaller deployment options like GPT-4.1 Nano starting at $0.10 per million input tokens.

Best for Gpt-4.1

  • Workloads requiring a verified 1M token input context window via API
  • Generative applications requiring lower output token costs at $8.00 per million output tokens
  • Deployments needing size-tiered edge or lightweight models like GPT-4.1 Mini and GPT-4.1 Nano starting at $0.10 per million input tokens
  • Fast direct-inference coding workloads requiring up to 40% faster execution than GPT-4o and GPT-4.5

Best for Gpt-5.1

  • Complex reasoning, math, and scientific tasks requiring dynamic adaptive thinking (94.0% on AIME 2025 and 87.3% on GPQA Diamond)
  • Input-heavy architectures leveraging a lower input cost of $1.25 per million input tokens
  • Applications needing integrated native web search and 8 customizable personality profiles
  • High-end code synthesis requiring advanced reasoning (86.8% on LiveCodeBench)

When not to compare directly

Do not compare GPT-4.1 and GPT-5.1 directly when evaluating large-context capabilities until GPT-5.1's exact context limits (conflicting between 128K, 272K, 400K, and 128K-196K tokens) are officially verified, when evaluating subscription variants with platform-specific boundaries (such as GPT-4.1's 32,000-token cap for ChatGPT Plus vs 1M via API), or when deploying for medical decision-making as neither model provides verified medical evaluation or regulatory clearance in this analysis.

What are the key differences between Gpt-4.1 and Gpt-5.1?

  • Reasoning Architecture & Benchmark Performance

    GPT-5.1 utilizes dynamic adaptive reasoning to score 94.0% on AIME 2025 and 87.3% on GPQA Diamond, whereas GPT-4.1 relies on direct inference optimizations demonstrated by a 21.4% gain on SWE-bench Verified.

    Gpt-4.1: GPT-4.1 is optimized for coding, instruction following, and complex programming, achieving a 21.4% improvement on the SWE-bench Verified benchmark over previous iterations while operating up to 40% faster than GPT-4o and GPT-4.5 [7, 9].

    Gpt-5.1: GPT-5.1 incorporates dynamic adaptive reasoning that adjusts thinking time to question complexity, achieving high benchmark evaluations including 94.0% on AIME 2025, 87.3% on GPQA Diamond, and 86.8% on LiveCodeBench [2, 4].

    Scores — Gpt-4.1: 7.2/10, Gpt-5.1: 9.4/10

    Determines how effectively each model handles complex problem-solving, mathematics, programming, and nuanced decision-making.

    Sources: GPT-5.1 - API, Specs, Playground & Pricing, OpenAI's GPT 4.1 in 7 Minutes

  • Context Window & Output Limits

    GPT-4.1 provides an established 1M token input context window with up to 33K output tokens, whereas GPT-5.1 has conflicting context specifications ranging from 128K up to 400,000 tokens and a 128K output limit.

    Gpt-4.1: OpenAI GPT-4.1 provides a 1M token context window via API with an output limit of up to 33K (or 32.8K) tokens, though its context is capped at 32,000 tokens for ChatGPT Plus users.

    Gpt-5.1: OpenAI GPT-5.1 features conflicting context window specifications across sources (128K, 272K, 400,000, or 128,000–196,000 tokens) alongside a listed 128K maximum output limit that was noted as unannounced in early API assessments.

    Scores — Gpt-4.1: 8.5/10, Gpt-5.1: 6.5/10

    Dictates the volume of input data, documentation, or codebases the model can process in a single prompt and the maximum length of generated outputs.

    Sources: GPT-4.1 Supports a 1M Token Context—Why Is ChatGPT ..., GPT 4.1 by OpenAI — Pricing, Specs & API Access

  • Model Family Variants & Personalization

    While GPT-4.1 segments its family into size tiers including flagship, Mini, and Nano models starting at $0.10 per million input tokens, GPT-5.1 uses functional Instant and Thinking modes alongside 8 customizable personality profiles.

    Gpt-4.1: OpenAI's GPT-4.1 series provides deployment flexibility across distinct size-tiered models, including the flagship GPT-4.1, GPT-4.1 Mini, GPT-4.1 Nano, and GPT 4.1 Nano 2025 04 14, with API rates starting at $0.10 per million input tokens for Nano up to $2.00 for the flagship [3].

    Gpt-5.1: GPT-5.1 structures its family around dynamic functional execution modes—GPT-5.1 Instant and GPT-5.1 Thinking—and provides 8 customizable personality profiles for tailored conversational interaction, priced at $1.25 per million input tokens [2, 4].

    Scores — Gpt-4.1: 8/10, Gpt-5.1: 8.5/10

    Influences deployment flexibility, latency management, and adaptability for specific user interaction styles or lightweight edge scenarios.

    Sources: GPT 4.1 by OpenAI — Pricing, Specs & API Access, GPT-5.1 - API, Specs, Playground & Pricing

  • API Pricing & Cost Efficiency

    GPT-4.1 costs $8.00 per million output tokens compared to $10.00 for GPT-5.1, while GPT-5.1 offers cheaper input processing at $1.25 per million tokens versus $2.00 for GPT-4.1.

    Gpt-4.1: GPT-4.1 is priced at $2.00 per million input tokens and $8.00 per million output tokens, offering lower output costs for generative workloads.

    Gpt-5.1: GPT-5.1 is priced at $1.25 per million input tokens and $10.00 per million output tokens, offering lower input costs for processing large prompts.

    Scores — Gpt-4.1: 7.5/10, Gpt-5.1: 7.5/10

    Directly impacts operational costs when scaling production workloads across high-volume input processing and output token generation.

    Sources: GPT 4.1 by OpenAI — Pricing, Specs & API Access, GPT-5.1 - API, Specs, Playground & Pricing

  • Developer Tooling & Multimodal Support

    GPT-5.1 explicitly integrates built-in web search alongside its vision, tool use, function calling, and structured JSON output capabilities, whereas GPT-4.1's provided tooling features specify vision, prompt caching, and structured outputs without web search.

    Gpt-4.1: GPT-4.1 supports developer tooling and multimodality with vision, function calling, prompt caching, structured outputs/response schemas, and a 1 million token context window (with up to 32.8K/33K output tokens), but its evidence does not confirm native web search integration.

    Gpt-5.1: GPT-5.1 includes multimodal text and image inputs alongside developer tooling for function calling, structured JSON output, prompt caching, web search integration, tool use, and 8 customizable personalities.

    Scores — Gpt-4.1: 8.2/10, Gpt-5.1: 9.4/10

    Affects ease of integration into agentic workflows, structured application pipelines, and visual understanding tasks.

    Sources: Support for GPT 5.1 · Issue #879 · enricoros/big-AGI, GPT 4.1 by OpenAI — Pricing, Specs & API Access

What are the pros and cons of Gpt-4.1 vs Gpt-5.1?

Gpt-4.1

Strengths

  • GPT-4.1 is optimized for coding, instruction following, and complex programming, achieving a 21.4% improvement on the SWE-bench Verified benchmark over previous iterations while operating up to 40% faster than GPT-4o and GPT-4.5.
  • GPT-4.1 provides an established 1M token input context window via API with an output limit of up to 33K (or 32.8K) tokens.
  • The GPT-4.1 series provides deployment flexibility across distinct size-tiered models—including flagship GPT-4.1, GPT-4.1 Mini, GPT-4.1 Nano, and GPT 4.1 Nano 2025 04 14—with API rates starting at $0.10 per million input tokens for Nano.
  • GPT-4.1 offers lower output costs for generative workloads, priced at $8.00 per million output tokens compared to $10.00 per million output tokens for GPT-5.1.
  • GPT-4.1 supports developer tooling and multimodality including vision, function calling, prompt caching, and structured outputs/response schemas.

Weaknesses

  • GPT-4.1's context window is capped at 32,000 tokens for ChatGPT Plus users compared to its 1M token API capacity.
  • GPT-4.1 features higher input costs at $2.00 per million input tokens compared to GPT-5.1's $1.25 per million input tokens.
  • GPT-4.1's provided feature specifications do not confirm native web search integration.

Gpt-5.1

Strengths

  • GPT-5.1 incorporates dynamic adaptive reasoning that adjusts thinking time to question complexity, scoring 94.0% on AIME 2025, 87.3% on GPQA Diamond, and 86.8% on LiveCodeBench.
  • GPT-5.1 offers lower input costs for processing large prompts, priced at $1.25 per million input tokens compared to $2.00 per million input tokens for GPT-4.1.
  • GPT-5.1 structures its family around dynamic functional execution modes (GPT-5.1 Instant and GPT-5.1 Thinking) and provides 8 customizable personality profiles for tailored conversational interaction.
  • GPT-5.1 supports a listed 128K maximum output token limit.
  • GPT-5.1 integrates developer features and multimodality including text and image inputs, function calling, structured JSON output, prompt caching, tool use, and built-in web search integration.

Weaknesses

  • GPT-5.1 has conflicting context window specifications across sources, with conflicting values reported at 128K, 272K, 400,000, or 128,000–196,000 tokens.
  • GPT-5.1 carries higher output generation costs at $10.00 per million output tokens compared to GPT-4.1's $8.00 per million output tokens.

Where does this data come from?

  1. GPT-4.1 Supports a 1M Token Context—Why Is ChatGPT ...
  2. Support for GPT 5.1 · Issue #879 · enricoros/big-AGI
  3. GPT 4.1 by OpenAI — Pricing, Specs & API Access
  4. GPT-5.1 - API, Specs, Playground & Pricing
  5. Introducing GPT-4.1 in the API
  6. GPT-5.1: A smarter, more conversational ChatGPT
  7. Putting GPT-4.1 to the Test: Coding Performance and ...
  8. GPT-5.1 Model | OpenAI API
  9. OpenAI's GPT 4.1 in 7 Minutes
  10. GPT 5.1 API Deep Dive
  11. The Complete Guide to GPT-4.1: Models, Performance ...
  12. GPT-5.1: Advanced Model With Strong Features and ...
  13. OpenAI's O4 and GPT‑4.1: A New Chapter in AI Language ...
  14. GPT-5.1 - API Pricing & Benchmarks
  15. GPT-4.1 Explained: Features, Model Types, Performance ...
  16. OpenAI GPT‑5.1: A Faster, Smarter, More Personal ChatGPT ...

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