Side-by-side technical and economic comparison between OpenAI's GPT-5.6 Terra and Google's Gemini 3.8 Flash.
| Metric | GPT-5.6 Terra | Gemini 3.8 Flash | Advantage |
|---|---|---|---|
| Provider Organization | OpenAI | — | |
| Standard Input / 1M | $2.00 | $0.75 | Gemini 3.8 Flash (63% lower) |
| Cached Input / 1M | $0.20 | $0.075 | Gemini 3.8 Flash lower |
| Output / 1M | $12.00 | $3.75 | Gemini 3.8 Flash lower |
| Context Window | 1.05M | 1.05M | GPT-5.6 Terra (1.05M) |
| Max Generation Tokens | 16.4k | 16.4k | GPT-5.6 Terra |
| Tokenizer Family | OpenAI o200k_base (200k vocabulary) | Google Gemini SentencePiece (256k vocabulary) | — |
| Workload (per month) | GPT-5.6 Terra | Gemini 3.8 Flash |
|---|---|---|
| Chatbot10k requests · 500 in / 200 out | $34.00 | $11.25 |
| RAG app100k requests · 8,000 in / 1,200 out | $3,040.00 | $1,050.00 |
| Coding agent100k requests · 12,000 in / 2,000 out | $4,800.00 | $1,650.00 |
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 Flash when looking for Google's tooling integration, specific context window depth (1.05M tokens), or when output generation volume favors its $3.75/M rate.
At a typical 3:1 input-to-output token mix, Gemini 3.8 Flash is about 67% cheaper than GPT-5.6 Terra. GPT-5.6 Terra costs $2 per 1M input and $12 per 1M output tokens; Gemini 3.8 Flash costs $0.75 and $3.75.
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 Flash: yes, cached input costs $0.075/1M.