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GPT-5.5 vs o4

A complete head-to-head: pricing, context window, benchmarks, modality coverage, and openness, with a programmatic verdict synthesized from the underlying data.

Updated

GPT-5.5 specs · o4 specs
Verdict by category
  • PriceTie

    Neither model publishes per-token API pricing.

  • Context windowGPT-5.5

    GPT-5.5 accepts 400K tokens vs 200K, 2.0× the room for long documents and codebases.

  • BenchmarksTie

    No directly comparable public benchmarks are available for both models, check the spec sheets for individual scores.

  • ModalitiesGPT-5.5

    GPT-5.5 supports 3 modalities (text, vision, audio) vs 2 for o4.

  • OpennessTie

    Both are closed-weight, API-only.

On balance GPT-5.5 edges ahead, winning 2 of 5 categories against o4's 0. Neither model publishes per-token API pricing. GPT-5.5 accepts 400K tokens vs 200K, 2.0× the room for long documents and codebases.

No directly comparable public benchmarks are available for both models, check the spec sheets for individual scores. They differ in modality coverage, GPT-5.5 handles text, vision, audio while o4 handles text, vision, which can be the deciding factor before you even look at benchmarks. Both are closed-weight, API-only.

GPT-5.5 is the newer of the two, released 3 months after o4, which usually means a more recent knowledge cutoff and updated safety post-training. GPT-5.5 is usually picked for agents and tool use workloads, while o4 sees more deployments in reasoning and math. If pricing matters more than every last benchmark point, run the numbers in the calculator below before committing.

Side-by-side specs

SpecGPT-5.5o4
ProviderOpenAIOpenAI
ReleasedMar 2026Dec 2025
Modalitiestext, vision, audiotext, vision
Context window400K tokens200K tokens
Max output,,
Input · 1MPricing not publishedPricing not published
Output · 1MPricing not publishedPricing not published
Knowledge cutoff,,
Open weightsNoNo
API availableYesYes

Pricing at scale

What you'd actually pay at typical workloads. Numbers come from each model's published per-million-token rates.

  • Light usage, 100k in / 50k out per day, vs ,
  • Heavy usage, 1M in / 500k out per day, vs ,
  • RAG workload, 5M in / 200k out per day, vs ,

Light usage, 100k in / 50k out per day: pricing not directly comparable (one or both models are missing public per-token rates). Heavy usage, 1M in / 500k out per day: pricing not directly comparable (one or both models are missing public per-token rates). RAG workload, 5M in / 200k out per day: pricing not directly comparable (one or both models are missing public per-token rates).

Price calculator

Estimated spend for the listed models at your usage. Numbers are derived from each model's published per-million-token rates.

  • GPT-5.5Pricing unavailable
  • o4Pricing unavailable

Benchmarks compared

Only sourced numbers. Where a benchmark is missing for one model we show the available value rather than fabricating the other.

Benchmark scores not yet available. We only publish numbers we can source from official model cards or independent leaderboards, see methodology.
Pick GPT-5.5 if

GPT-5.5 fits when…

  • Industry-leading tool-use and function-calling reliability
  • Strong end-to-end agent performance across SWE-bench and GAIA
  • Wide ecosystem support, ChatGPT, Realtime API, Responses API
  • Long-context tasks, handles 400K tokens vs 200K for o4.
  • Multimodal needs covering audio.
Pick o4 if

o4 fits when…

  • Exceptional performance on hard math and reasoning benchmarks
  • Good at multi-step planning and verification
  • Strong scientific reasoning
Don't want either?

Consider GPT-5

OpenAI's unified flagship combining GPT-line breadth with built-in reasoning, replacing both GPT-4o and the o-series for most users.

See GPT-5 specsGPT-5.5 vs GPT-5o4 vs GPT-5

Frequently asked

  • Is GPT-5.5 or o4 cheaper?
    Per-token pricing isn't published for at least one of these models, check each model's spec page for current rates.
  • Which has the larger context window?
    GPT-5.5 accepts 400K tokens vs 200K for o4.
  • Is GPT-5.5 or o4 better for coding?
    Both GPT-5.5 and o4 are competitive on coding benchmarks. See each model's individual spec page for HumanEval and SWE-bench scores where published. For an opinionated pick, consult our Best LLM for Coding ranking.
  • Are either of these models open source?
    Neither model ships open weights, both are accessible only via their respective providers' APIs.
  • When were GPT-5.5 and o4 released?
    GPT-5.5 was released by OpenAI on 2026-03-01. o4 was released by OpenAI on 2025-12-15.
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