GPT-5.6 vs Gemini 3.5 Flash: API pricing
OpenAI's GPT-5.6 against Google (Gemini API)'s Gemini 3.5 Flash on price alone — per-token rates, caching, and context window. Run your own workload through both with the calculator below; capability differences are yours to judge on your evals.
| GPT-5.6 | Gemini 3.5 Flash | |
|---|---|---|
| Input / 1M tokens | $5.00 | $1.50 |
| Cached input / 1M | $0.50 | $0.15 |
| Output / 1M tokens | $30.00 | $9.00 |
| Context window | 1M | 1M |
| Max output | 125K | 66K |
| Vendor | OpenAI | Google (Gemini API) |
Prices last synced Aug 20, 2026 from the LiteLLM community price catalog — the same catalog Marginal prices real usage events against, refreshed daily. Spot an error? Tell us.
Price takeaways
- Input: Gemini 3.5 Flash is 3x cheaper.
- Output: Gemini 3.5 Flash is 3x cheaper.
- Cached input: Gemini 3.5 Flash is 3x cheaper.
- Ratios shift with workload shape — output-heavy traffic weights the output rate, cache-friendly traffic weights the cached rate. The calculator below does the arithmetic on your numbers.
Your workload on both
Your monthly workload
Cache hit rate = share of input tokens served from the provider's prompt cache, billed at the model's cached-input price. Estimates use standard per-token rates — batch discounts, service tiers, and long-context surcharges are not applied.
| Model | Input | Cached input | Output | Per request | Monthly |
|---|---|---|---|---|---|
| Gemini 3.5 Flashcheapest | $900 | $60.00 | $2,250 | $0.00642 | $3,210 |
| GPT-5.6 | $3,000 | $200 | $7,500 | $0.021 | $10,700 |
Related comparisons
Switching models? Watch the bill move in real time.
Marginal prices every call against that day's rates, so an A/B between these two shows up as dollars per customer and feature — not a surprise at month end.