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GPT-5 mini 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 mini specs · Phi-3.5 Medium specs
Verdict by category
  • PriceGPT-5 mini

    GPT-5 mini publishes pricing ($2.00 / 1M output tokens) while Phi-3.5 Medium does not.

  • Context windowGPT-5 mini

    GPT-5 mini 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 mini

    GPT-5 mini 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 mini is API-only.

On balance GPT-5 mini edges ahead, winning 3 of 5 categories against Phi-3.5 Medium's 1. GPT-5 mini publishes pricing ($2.00 / 1M output tokens) while Phi-3.5 Medium does not. GPT-5 mini 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 mini 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 mini is API-only.

GPT-5 mini is the newer of the two, released 12 months after Phi-3.5 Medium, which usually means a more recent knowledge cutoff and updated safety post-training. GPT-5 mini is usually picked for code completion and customer support 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 miniPhi-3.5 Medium
ProviderOpenAIMicrosoft
ReleasedAug 2025Aug 2024
Modalitiestext, vision, audiotext
Context window400K tokens128K tokens
Max output128K tokens,
Input · 1M$0.25 / 1M tokensPricing not published
Output · 1M$2.00 / 1M tokensPricing not published
Knowledge cutoff2024-09,
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$3.75 vs ,
  • Heavy usage, 1M in / 500k out per day$37.50 vs ,
  • RAG workload, 5M in / 200k out per day$49.50 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 mini$0.125
  • 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 miniPhi-3.5 Medium
  • MMLU,78.9
Pick GPT-5 mini if

GPT-5 mini fits when…

  • Excellent price-quality ratio for production workloads
  • Fast first-token latency
  • Same tool-use API surface as flagship
  • 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-5.5

OpenAI's mid-cycle GPT-5 refresh, improved reasoning, tool use, and multimodal grounding over the 2025 launch.

See GPT-5.5 specsGPT-5 mini vs GPT-5.5Phi-3.5 Medium vs GPT-5.5

Frequently asked

  • Is GPT-5 mini 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 mini accepts 400K tokens vs 128K for Phi-3.5 Medium.
  • Is GPT-5 mini or Phi-3.5 Medium better for coding?
    Both GPT-5 mini 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 mini is API-only.
  • When were GPT-5 mini and Phi-3.5 Medium released?
    GPT-5 mini was released by OpenAI on 2025-08-07. Phi-3.5 Medium was released by Microsoft on 2024-08-20.
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