ZMIME
Comparison · 2 models · Updated Nov 2, 2026

GPT OSS 20B vs Gemini 2.5 Flash

Gemini 2.5 Flash comes out ahead, 66 to 61 on our weighted score, though GPT OSS 20B is 7.4× cheaper per token.

  1. OpenAI

    GPT OSS 20B

    Released Aug 5, 2025

    61/100
    • ECI137.8
    • Price$0.07 / $0.25
    • Context131K
    Full specs Remove GPT OSS 20B
  2. Our pick

    Google

    Gemini 2.5 Flash

    Released Jun 17, 2025

    66/100
    • ECI140.6
    • Price$0.30 / $2.50
    • Context1.05M
    Full specs Remove Gemini 2.5 Flash

  3. Add a model

    Make it a three-way comparison.

01 — Verdict

Gemini 2.5 Flash is our pick

Gemini 2.5 Flash is the better all-round choice, scoring 66/100 against GPT OSS 20B (61). It leads on capability, inputs & features and context window. GPT OSS 20B wins on price. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.

  • CapabilityGemini 2.5 FlashCapabilities Index (ECI): Gemini 2.5 Flash 140.6 · GPT OSS 20B 137.8
  • Lowest priceGPT OSS 20BGPT OSS 20B $0.115 · Gemini 2.5 Flash $0.85 per 1M tokens (3:1 blend)
  • Longest contextGemini 2.5 FlashGemini 2.5 Flash 1,048,576 · GPT OSS 20B 131,072 tokens
  • Widest inputsGemini 2.5 FlashGPT OSS 20B: Text · Gemini 2.5 Flash: Text, Images, PDFs, Audio, Video
  • Self-hostingGPT OSS 20BPublishes downloadable weights
How the score is built
MeasureWeightGPT OSS 20BGemini 2.5 Flash
CapabilityCapabilities Index (ECI)50%6165
Price25%9051
Inputs & features15%35100
Context window10%2561
Overall100%61/10066/100
02 — Side by side

Every spec in one table

Highlighted cells lead their row. Dashes mean the data is not published.

GPT OSS 20B vs Gemini 2.5 Flash specifications side by side
SpecificationGPT OSS 20BOpenAIGemini 2.5 FlashGoogle
Capability
Capabilities Index (ECI)137.8140.6 (best)
ECI rank#122 of 165#110 of 165 (best)
GPQA DiamondGraduate-level science questions60.8%—
OTIS Mock AIME 2024–2025Competition mathematics65.3%—
Price per million tokens
Input$0.07 (best)$0.30
Output$0.25 (best)$2.50
Cached input—$0.03
Blended (3:1)$0.115 (best)$0.85
Long-context rateSame rateSame rate
Price sourceMedian of 37 providersOfficial Google API
Limits
Context window131,072 tokens1,048,576 tokens (best)
Max output32,768 tokens65,536 tokens (best)
Inputs and features
TextYesYes
ImagesNoYes
PDFsNoYes
AudioNoYes
VideoNoYes
ReasoningYesYes
Tool callingYesYes
Structured outputNoYes
Availability
WeightsOpenProprietary
API model ID—gemini-2.5-flash
API providers41 (best)32
ReleasedAug 5, 2025Jun 17, 2025
Knowledge cutoffJun 2024Jan 2025
03 — Cost

What would a month cost?

Enter your expected volume in millions of tokens. List prices only; caching and batch discounts would lower these.

  • GPT OSS 20B$1.20
  • Gemini 2.5 Flash$8.00
04 — Questions

Which should you choose?

Which is better: GPT OSS 20B or Gemini 2.5 Flash?

Gemini 2.5 Flash is the better all-round choice, scoring 66/100 against GPT OSS 20B (61). It leads on capability, inputs & features and context window. GPT OSS 20B wins on price. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.

Which is cheaper, GPT OSS 20B or Gemini 2.5 Flash?

GPT OSS 20B is cheaper at $0.07 input / $0.25 output per million tokens (median across 37 API providers). Gemini 2.5 Flash costs $0.30 input / $2.50 output per million tokens (official Google API price). At a typical mix of three input tokens to one output token, that is $0.115 per million tokens for GPT OSS 20B versus $0.85 for Gemini 2.5 Flash (7.4× as much).

Which scores higher on benchmarks?

Gemini 2.5 Flash scores higher on the Capabilities Index (ECI): Gemini 2.5 Flash 140.6 (#110 of 165) and GPT OSS 20B 137.8 (#122 of 165). The confidence ranges of the top two overlap (138.4–142.1 vs 133.1–139.7), so treat the gap as small.

Which is better for coding?

There are no published SWE-bench Verified results for GPT OSS 20B and Gemini 2.5 Flash yet, so there is no like-for-like coding score. On overall capability, Gemini 2.5 Flash leads, which tends to carry over to coding, but test on your own codebase. Both support tool calling for agent workflows.

Which has the bigger context window?

Gemini 2.5 Flash has the largest context window at 1,048,576 tokens, against 131,072 for GPT OSS 20B. Maximum output per response: GPT OSS 20B up to 32,768, Gemini 2.5 Flash up to 65,536 tokens.

Which can read images, PDFs, audio or video?

GPT OSS 20B accepts text; Gemini 2.5 Flash accepts text, images, PDFs, audio and video. Gemini 2.5 Flash handles the widest range of inputs.

Are any of these open source?

GPT OSS 20B publishes its weights and can be self-hosted; Gemini 2.5 Flash is proprietary.

Which is newer?

GPT OSS 20B is the newest, released Aug 5, 2025. Gemini 2.5 Flash came out Jun 17, 2025. Knowledge cutoff: GPT OSS 20B Jun 2024, Gemini 2.5 Flash Jan 2025.

How do you decide the winner?

Each model gets a 0–100 score on capability (50%, independent benchmark results); price (25%, blended price per million tokens (3 input : 1 output), log scale); inputs & features (15%, image, PDF, audio and video input, tool calling, structured output and reasoning); context window (10%, maximum tokens per request, log scale). Dimensions missing for any model are dropped and the remaining weights rescaled, so every model is judged on the same evidence. Specs and prices come from public model listings and the labs’ own API pages; capability scores come from independent benchmark runs. Data updated Nov 2, 2026.

05 — Keep comparing

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