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GPT-5.5 vs Phi-3.5 Medium

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 · Phi-3.5 Medium specs
Verdict by category
  • PriceTie

    Neither model publishes per-token API pricing.

  • Context windowGPT-5.5

    GPT-5.5 accepts 400K tokens vs 128K, 3.1× 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 1 for Phi-3.5 Medium.

  • OpennessPhi-3.5 Medium

    Phi-3.5 Medium ships open weights (MIT); GPT-5.5 is API-only.

On balance GPT-5.5 edges ahead, winning 2 of 5 categories against Phi-3.5 Medium's 1. Neither model publishes per-token API pricing. GPT-5.5 accepts 400K tokens vs 128K, 3.1× 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 Phi-3.5 Medium handles text, which can be the deciding factor before you even look at benchmarks. Phi-3.5 Medium ships open weights (MIT); GPT-5.5 is API-only.

GPT-5.5 is the newer of the two, released 19 months after Phi-3.5 Medium, 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 Phi-3.5 Medium sees more deployments in on device and edge deployment. If pricing matters more than every last benchmark point, run the numbers in the calculator below before committing.

Side-by-side specs

SpecGPT-5.5Phi-3.5 Medium
ProviderOpenAIMicrosoft
ReleasedMar 2026Aug 2024
Modalitiestext, vision, audiotext
Context window400K tokens128K tokens
Max output,,
Input · 1MPricing not publishedPricing not published
Output · 1MPricing not publishedPricing not published
Knowledge cutoff,,
Open weightsNoYes (MIT)
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
  • Phi-3.5 MediumPricing unavailable

Benchmarks compared

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

GPT-5.5Phi-3.5 Medium
  • MMLU,78.9
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 128K for Phi-3.5 Medium.
  • Multimodal needs covering vision, audio.
Pick Phi-3.5 Medium if

Phi-3.5 Medium fits when…

  • MIT license
  • 128k context
  • Strong reasoning at 14B
  • Self-hosting and on-prem requirements, open weights (MIT).
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-5Phi-3.5 Medium vs GPT-5

Frequently asked

  • Is GPT-5.5 or Phi-3.5 Medium 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 128K for Phi-3.5 Medium.
  • Is GPT-5.5 or Phi-3.5 Medium better for coding?
    Both GPT-5.5 and Phi-3.5 Medium 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?
    Phi-3.5 Medium ships open weights (MIT). GPT-5.5 is API-only.
  • When were GPT-5.5 and Phi-3.5 Medium released?
    GPT-5.5 was released by OpenAI on 2026-03-01. Phi-3.5 Medium was released by Microsoft on 2024-08-20.
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