# GPT-4.5 vs GPT-OSS 20B

> Side-by-side benchmark comparison for GPT-4.5 and GPT-OSS 20B across agentic, coding, multimodal, knowledge, reasoning, multilingual, and math tasks.

- Canonical page: https://benchlm.ai/compare/gpt-4-5-vs-gpt-oss-20b
- Last updated: October 14, 2026

- Shared sourced benchmarks: 2
- HTML indexing: indexable
- Ranking lane: BenchAlign v5.8

## Quick Verdict

Evidence is too thin for a benchmark verdict: GPT-4.5 and GPT-OSS 20B share only 2 sourced benchmark rows.

## Summary

- Only 2 shared sourced benchmark rows are available. That is not enough for a broad capability verdict, so this mirror does not name an overall winner.
- GPT-OSS 20B has the lower published output-token price.

## Model Snapshot

| Property | GPT-4.5 | GPT-OSS 20B |
|----------|----------|----------|
| Creator | OpenAI | OpenAI |
| Type | Proprietary | Open Weight |
| Reasoning | Non-Reasoning | Non-Reasoning |
| Context | 128K | 128K |
| Independent public score (not head-to-head) | null | 33.29 |
| Benchmarks Covered | 6 | 7 |
| Pricing (input/output) | $75.00 / $150.00 | $0.00 / $0.00 |

## Category Breakdown

### Agentic

- Winner: Insufficient shared evidence
- GPT-4.5 public-lane score: Coming soon
- GPT-OSS 20B public-lane score: 15.5 (Estimated · #112/124)

### Coding

- Winner: Insufficient shared evidence
- GPT-4.5 public-lane score: Coming soon
- GPT-OSS 20B public-lane score: 18.2 (Estimated · #121/148)

| Benchmark | GPT-4.5 | GPT-OSS 20B | Winner |
|-----------|-----------|-----------|--------|
| HumanEval | 88.6% | Coming soon | Coming soon |
| SWE-bench Verified | Coming soon | 60.7% | Coming soon |
| React Native Evals | Coming soon | 71% | Coming soon |

### Reasoning

- Winner: Insufficient shared evidence
- GPT-4.5 public-lane score: Coming soon
- GPT-OSS 20B public-lane score: 49.7 (Unranked · 2 rankable rows)

| Benchmark | GPT-4.5 | GPT-OSS 20B | Winner |
|-----------|-----------|-----------|--------|
| DROP | 83.4% | Coming soon | Coming soon |

### Knowledge

- Winner: Insufficient shared evidence
- GPT-4.5 public-lane score: Coming soon
- GPT-OSS 20B public-lane score: 34 (Supported · #137/181)

| Benchmark | GPT-4.5 | GPT-OSS 20B | Winner |
|-----------|-----------|-----------|--------|
| MMLU | 90.8% | 85.3% | GPT-4.5 |
| GPQA | 69.5% | 71.5% | GPT-OSS 20B |
| SimpleQA | 62.5% | Coming soon | Coming soon |
| HLE | Coming soon | 10.9% | Coming soon |

### Multilingual

- Winner: Insufficient shared evidence
- GPT-4.5 public-lane score: Coming soon
- GPT-OSS 20B public-lane score: Coming soon

| Benchmark | GPT-4.5 | GPT-OSS 20B | Winner |
|-----------|-----------|-----------|--------|
| MGSM | 86.9% | Coming soon | Coming soon |

### Instruction Following

- Winner: Insufficient shared evidence
- GPT-4.5 public-lane score: Coming soon
- GPT-OSS 20B public-lane score: 79.2 (#57/128)

### Mathematics

- Winner: Insufficient shared evidence
- GPT-4.5 public-lane score: Coming soon
- GPT-OSS 20B public-lane score: Coming soon

| Benchmark | GPT-4.5 | GPT-OSS 20B | Winner |
|-----------|-----------|-----------|--------|
| AIME 2024 | Coming soon | 92.1% | Coming soon |
| AIME 2025 | Coming soon | 91.7% | Coming soon |

## FAQ

### Is there enough evidence to pick between GPT-4.5 and GPT-OSS 20B?

Not yet. The models share only 2 sourced benchmark rows, so this mirror reports the available measurements and metadata without naming a broad winner.

### What can I compare safely on this page?

Published pricing, context windows, model type, and individual shared benchmark rows are directly comparable. Independent overall scores and non-overlapping benchmark coverage are labeled separately and should not be read as a controlled head-to-head result.

## Related Comparisons

- [GPT-4.5 vs GPT-OSS 120B](/compare/gpt-4-5-vs-gpt-oss-120b)
- [GPT-OSS 20B vs GPT-OSS 120B](/compare/gpt-oss-120b-vs-gpt-oss-20b)
- [GPT-4.5 vs Claude Opus 5.5](/compare/claude-opus-5-5-vs-gpt-4-5)
- [GPT-OSS 20B vs Claude Opus 5.5](/compare/claude-opus-5-5-vs-gpt-oss-20b)

## Explore More

- [GPT-4.5 profile](/models/gpt-4-5)
- [GPT-OSS 20B profile](/models/gpt-oss-20b)
- [Compare Pricing](/llm-pricing)
- [Alternative Finder](/tools/alternative-finder)
- [LLM Selector](/tools/llm-selector)
- [Overall Rankings](/best/overall)