Claude Opus 4.5 vs GPT-OSS 20B
Side-by-side benchmark comparison across coding, math, reasoning, speed, and pricing.
Claude Opus 4.5 by Anthropic and GPT-OSS 20B by OpenAI are evenly matched across 10 benchmarks. This head-to-head comparison covers coding, math, reasoning, speed, and pricing metrics from our benchmark data.
Category-by-Category Breakdown
Coding: In coding, Claude Opus 4.5 scores 1242 on Design Arena ELO compared to GPT-OSS 20B's 906, while Claude Opus 4.5 scores 1259 on Website Arena ELO compared to GPT-OSS 20B's 865.
Reasoning: In reasoning, Claude Opus 4.5 scores 86.5% on GPQA Diamond compared to GPT-OSS 20B's 66.5%, while Claude Opus 4.5 scores 77.0% on τ²-Bench Airline compared to GPT-OSS 20B's 51.4%.
Context: In context, Claude Opus 4.5 scores 200K on Context Length compared to GPT-OSS 20B's 131K.
Pricing Comparison
Claude Opus 4.5 costs $5.0/1M input tokens and $25.0/1M output tokens, while GPT-OSS 20B costs $0.03/1M input and $0.13/1M output. GPT-OSS 20B is the more affordable option for API usage.
Speed Comparison
Claude Opus 4.5 generates output at 50 tok/s compared to GPT-OSS 20B's 312 tok/s, and the time to first token is 1700 ms for Claude Opus 4.5 versus 470 ms for GPT-OSS 20B. GPT-OSS 20B delivers faster throughput.
Verdict
GPT-OSS 20B leads across the board in affordability, speed, making it the stronger overall choice in this comparison.
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Claude Opus 4.5 vs GPT-OSS 20B — FAQ
Which is better, Claude Opus 4.5 or GPT-OSS 20B?
Claude Opus 4.5 and GPT-OSS 20B are evenly matched across benchmarks. The best choice depends on your specific priorities such as coding ability, speed, or pricing.
How does Claude Opus 4.5 compare to GPT-OSS 20B for coding?
SWE-bench Verified data is not available for both models. Check the detailed comparison charts above for other coding-related metrics.
Is Claude Opus 4.5 cheaper than GPT-OSS 20B?
Yes, GPT-OSS 20B is cheaper. Claude Opus 4.5 costs $5.0/1M input and $25.0/1M output tokens. GPT-OSS 20B costs $0.03/1M input and $0.13/1M output tokens.
Which is faster, Claude Opus 4.5 or GPT-OSS 20B?
GPT-OSS 20B is faster, generating output at 312 tok/s compared to 50 tok/s. Faster output speed means shorter wait times for API responses.
What benchmarks does the Claude Opus 4.5 vs GPT-OSS 20B comparison cover?
This comparison covers 10 benchmarks including GPQA Diamond, Output Speed, Time to First Token, Input Cost, Output Cost, Context Length, Cached Input Cost, Design Arena ELO, and more. Metrics span general intelligence, coding, math, reasoning, speed, and cost categories.