Model comparison
Gemini 2.5 Flash vs GPT-OSS 20B
Head-to-head evidence from 12 shared benchmark results across 6 categories. Overall scores shown here use the public BenchAlign v5 ranking lane.
Public leaderboard positions: Gemini 2.5 Flash #130 (Supported); GPT-OSS 20B #159 (Supported). Intervals and evidence labels describe ranking uncertainty, not a guarantee for a specific workload.
Evidence parity. Gemini 2.5 Flash and GPT-OSS 20B share 12 comparable benchmark results. 0 of 8 categories are comparable. 3 results are unique to Gemini 2.5 Flash; 6 to GPT-OSS 20B.
Updated July 20, 2026- Shared results
- 12
- Gemini 2.5 Flash only
- 3
- GPT-OSS 20B only
- 6
- Comparable categories
- 0 / 8
Benchmark data for Gemini 2.5 Flash and GPT-OSS 20B is coming soon on BenchLM.
Confidence note. This is a partial-evidence comparison with 12 shared benchmark results across 6 evidence categories; 0 of 8 categories currently have scoreable aggregates for both models. Treat the verdict as directional until coverage is more balanced.
Why this result
BenchLM has partial data for these models, but not enough overlapping benchmark coverage to produce a fair score-level comparison yet.
Gemini 2.5 Flash is priced at $0.30 input / $2.50 output per 1M tokens, versus $0.00 input / $0.00 output per 1M tokens for GPT-OSS 20B. Gemini 2.5 Flash has the larger context window at 1M, compared with 128K for GPT-OSS 20B.
Category breakdown
Exact category averages are shown below. Not measured means BenchLM does not have enough sourced public coverage for that model and category.
| Category | Gemini 2.5 Flash | Δ | GPT-OSS 20B |
|---|---|---|---|
| Math | Gemini 2.5 Flash4.7 | MarginNo overlap | GPT-OSS 20BNot measured |
Operational comparison
Runtime and commercial metrics are compared only when both models have a complete sourced value.
| Metric | Gemini 2.5 Flash | GPT-OSS 20B | Comparison |
|---|---|---|---|
| Input / output priceUSD per 1M tokens | Gemini 2.5 Flash$0.3 input / $2.5 output | GPT-OSS 20B$0 input / $0 output | GPT-OSS 20B has the lower combined listed price. |
| Generation speedtokens per second | Gemini 2.5 Flash221 tok/s | GPT-OSS 20B313 tok/s | GPT-OSS 20B has the higher measured throughput. |
| First-answer latencyseconds to first token | Gemini 2.5 Flash0.50 s | GPT-OSS 20B0.65 s | Gemini 2.5 Flash reaches the first token sooner. |
| Context windowmaximum listed tokens | Gemini 2.5 Flash1M | GPT-OSS 20B128K | Gemini 2.5 Flash lists the larger context window. |
Benchmark Deep Dive
Agentic5 benchmarks
Coding3 benchmarks
Reasoning2 benchmarks
Knowledge6 benchmarks
| Benchmark | Gemini 2.5 Flash | GPT-OSS 20B | Result |
|---|---|---|---|
| Artificial Analysis Intelligence IndexSource | 14.1% | 14.9% | GPT-OSS 20B leads |
| AA-GPQA DiamondSource | 68.3% | 68.8% | GPT-OSS 20B leads |
| AA-HLESource | 5.1% | 9.8% | GPT-OSS 20B leads |
| AA-Omniscience IndexSource | -42.0% | -63.9% | Gemini 2.5 Flash leads |
| AA-Omniscience AccuracySource | 26.5% | 15.5% | Gemini 2.5 Flash leads |
| AA-Omniscience Hallucination RateSource | 93.3% | 94.1% | Gemini 2.5 Flash leads |
Math2 benchmarks
Multimodal2 benchmarks
Inst. Following1 benchmarks
| Benchmark | Gemini 2.5 Flash | GPT-OSS 20B | Result |
|---|---|---|---|
| AA-IFBenchSource | 39.0% | 65.1% | GPT-OSS 20B leads |
Frequently Asked Questions (3)
Can I compare Gemini 2.5 Flash and GPT-OSS 20B on BenchLM yet?
Not fully yet. BenchLM is tracking both models, but the sourced benchmark breakdown for this comparison is still coming soon.
Why does this comparison show “coming soon”?
BenchLM only shows category winners and benchmark-level calls when we have sourced results that can be compared fairly. For these models, the public benchmark coverage is not complete enough yet.
What data is available for Gemini 2.5 Flash and GPT-OSS 20B today?
Gemini 2.5 Flash: $0.30 input / $2.50 output per 1M tokens GPT-OSS 20B: $0.00 input / $0.00 output per 1M tokens Both model pages still include creator, context window, reasoning mode, and other metadata while benchmark coverage fills in.
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