gpt-oss-20b (free) is free for input tokens while GPT-5.5 Pro costs $30 per 1M tokens.
API cost decision in 10 seconds
gpt-oss-20b (free) vs GPT-5.5 Pro
Pick gpt-oss-20b (free) for lower cost; pick GPT-5.5 Pro only if the larger context window matters more.
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Data confirmed:
Prices normalized to USD per 1M tokens
Sample workload: 1M input + 500K output
Budget verdict
Pick gpt-oss-20b (free) for lower cost; pick GPT-5.5 Pro only if the larger context window matters more.
On the standard 1M input plus 500K output workload, gpt-oss-20b (free) is estimated at $0 vs $120 for GPT-5.5 Pro, saving $120 (100% lower).
Cost-first pickgpt-oss-20b (free)
Context-first pickGPT-5.5 Pro
Sample savings$120100%
10x traffic gap$1200
GPT-5.5 Pro has more context, but gpt-oss-20b (free) saves $120 on the standard workload. At 10x that traffic, the same price gap is about $1200. Use the calculator below to replace the sample workload with your own token volume.
Cost sensitivity
Workload Sensitivity
gpt-oss-20b (free) stays cheaper across input-heavy, balanced, and output-heavy sample workloads.
| Workload shape | Token mix | Better pick | gpt-oss-20b (free) | GPT-5.5 Pro |
|---|---|---|---|---|
| Input-heavy / RAG | 5M input + 500K output | gpt-oss-20b (free) | $0 | $240 |
| Balanced workload | 1M input + 1M output | gpt-oss-20b (free) | $0 | $210 |
| Output-heavy chatbot | 1M input + 5M output | gpt-oss-20b (free) | $0 | $930 |
gpt-oss-20b (free) is free for output tokens while GPT-5.5 Pro costs $180 per 1M tokens.
GPT-5.5 Pro has 918.93K more context (8.01x larger).
gpt-oss-20b (free) is free for the standard workload while the other model is estimated at $120.
Estimate your workload cost
Your Workload Cost
This estimate uses normalized public API pricing per 1M tokens. It is a planning aid, not a billing quote. Verify provider pricing, limits, and terms before production use.
Quick Decision
gpt-oss-20b (free) has the lower input price; gpt-oss-20b (free) has the lower output price; GPT-5.5 Pro offers the larger context window. For the 1M input plus 500K output sample, gpt-oss-20b (free) is cheaper for the standard workload.
For a 1M input token plus 500K output token workload, the estimated API cost is $0 for gpt-oss-20b (free) and $120 for GPT-5.5 Pro.
Choose gpt-oss-20b (free) when you care most about lower input-token price, and lower output-token price.
Choose GPT-5.5 Pro when you care most about larger context window.
- On the standard 1M input plus 500K output workload, gpt-oss-20b (free) is estimated at $0 vs $120 for GPT-5.5 Pro, saving $120 (100% lower).
- gpt-oss-20b (free) is free for the standard workload while the other model is estimated at $120.
- gpt-oss-20b (free) is free for input tokens while GPT-5.5 Pro costs $30 per 1M tokens.
- gpt-oss-20b (free) is free for output tokens while GPT-5.5 Pro costs $180 per 1M tokens.
- GPT-5.5 Pro has 918.93K more context (8.01x larger).
| Feature | gpt-oss-20b (free) (OpenAI) | GPT-5.5 Pro (OpenAI) |
|---|---|---|
| Input Price prompt tokens per 1M | $0 | $30 |
| Completion Price per 1M tokens | $0 | $180 |
| Sample Workload Cost 1M input + 500K output | $0 | $120 |
| Context Window | 131.07K | 1.05M |
| Release Date | ||
| Popularity | #72 | #122 |
Use-Case Decision Matrix
| Use case | Better pick | Why |
|---|---|---|
| Budget-constrained production | gpt-oss-20b (free) | On the standard 1M input plus 500K output workload, gpt-oss-20b (free) is estimated at $0 vs $120 for GPT-5.5 Pro, saving $120 (100% lower). |
| High-volume input processing | gpt-oss-20b (free) | Lower prompt-token price matters most when prompts, retrieved passages, or documents dominate the bill. |
| Long responses and chatbots | gpt-oss-20b (free) | Lower output-token price matters most when assistants generate many completion tokens. |
| RAG or long-document work | GPT-5.5 Pro | A larger context window leaves more room for retrieved passages, conversation history, or source files. |
Related Alternatives
- gpt-oss-120b (free) can replace GPT-5.5 Pro when lower sample workload cost matters most: $0.
- gpt-oss-20b can replace GPT-5.5 Pro when lower sample workload cost matters most: $0.1.
- gpt-oss-120b can replace GPT-5.5 Pro when lower sample workload cost matters most: $0.13.
- gpt-oss-safeguard-20b can replace GPT-5.5 Pro when lower sample workload cost matters most: $0.22.
- Llama 4 Scout offers 10M context with $0.23 sample workload cost.
- Grok 4.20 offers 2M context with $2.5 sample workload cost.
- Grok 4.20 Multi-Agent offers 2M context with $5 sample workload cost.
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Cheaper alternatives
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Open OpenAI modelsgpt-oss-20b is an open-weight 21B parameter model released by OpenAI under the Apache 2.0 license. It uses a Mixture-of-Experts (MoE) architecture with 3.6B active parameters per forward pass, optimized for...
GPT-5.5 Pro is OpenAI’s high-capability model optimized for deep reasoning and accuracy on complex, high-stakes workloads. It features a 1M+ token context window (922K input, 128K output) with support for...