Side-by-side technical and economic comparison between OpenAI's GPT-5.6 Terra and Google's Gemini 3.8 Pro.
| Metric | GPT-5.6 Terra | Gemini 3.8 Pro | Advantage |
|---|---|---|---|
| Provider Organization | OpenAI | — | |
| Standard Input / 1M | $2.00 | $4.00 | GPT-5.6 Terra (50% lower) |
| Cached Input / 1M | $0.20 | $0.40 | GPT-5.6 Terra lower |
| Output / 1M | $12.00 | $18.00 | GPT-5.6 Terra lower |
| Context Window | 1.05M | 1.05M | GPT-5.6 Terra (1.05M) |
| Max Generation Tokens | 16.4k | 64k | Gemini 3.8 Pro |
| Tokenizer Family | OpenAI o200k_base (200k vocabulary) | Google Gemini SentencePiece (256k vocabulary) | — |
| Workload (per month) | GPT-5.6 Terra | Gemini 3.8 Pro |
|---|---|---|
| Chatbot10k requests · 500 in / 200 out | $34.00 | $56.00 |
| RAG app100k requests · 8,000 in / 1,200 out | $3,040.00 | $5,360.00 |
| Coding agent100k requests · 12,000 in / 2,000 out | $4,800.00 | $8,400.00 |
Standard rates, no caching or batch discounts. Model your own numbers below.
Opt for GPT-5.6 Terra when your engineering requirements prioritize OpenAI's ecosystem, specific tokenizer efficiencies (Exact BPE (o200k_base)), or when your expected prompt-to-completion ratios favor its $2/M input rate.
Opt for Gemini 3.8 Pro when looking for Google's tooling integration, specific context window depth (1.05M tokens), or when output generation volume favors its $18/M rate.
At a typical 3:1 input-to-output token mix, GPT-5.6 Terra is about 40% cheaper than Gemini 3.8 Pro. GPT-5.6 Terra costs $2 per 1M input and $12 per 1M output tokens; Gemini 3.8 Pro costs $4 and $18.
GPT-5.6 Terra has the larger context window: 1.05M tokens vs 1.05M.
GPT-5.6 Terra: yes, cached input costs $0.2/1M. Gemini 3.8 Pro: yes, cached input costs $0.4/1M.