o4-mini vs Gemini 3.5 Flash
Detailed pricing comparison and cost analysis.
Updated September 2026
Cost Simulator
| Feature | o4-mini | Gemini 3.5 Flash |
|---|---|---|
| Provider | OpenAI | |
| Input Price (1M) | $1.10 | $1.50 |
| Output Price (1M) | $4.40 | $9.00 |
| Context Window | 200,000 | 1,000,000 |
Verdict
o4-mini costs $1.10 per 1M input tokens and $4.40 per 1M output tokens. Gemini 3.5 Flash costs $1.50 per 1M input tokens and $9.00 per 1M output tokens. o4-mini is 27% cheaper on input tokens than Gemini 3.5 Flash. For output tokens, o4-mini is the more affordable option at $4.40/1M vs $9.00.
On context window, Gemini 3.5 Flash supports 1,000,000 tokens — meaning it can fit more conversation history, documents, or code in a single request. This matters for RAG pipelines, long document analysis, and agentic workflows where context builds up over many turns.
When to choose o4-mini
- ✓ You need the lowest input token cost ($ 1.10/1M)
- ✓ Your workload is output-heavy — o4-mini generates text cheaper
- ✓ You are already integrated with OpenAI
When to choose Gemini 3.5 Flash
- ✓ You need a larger context window (1,000,000 tokens)
- ✓ You are already integrated with Google
Use the calculator above to simulate your specific workload and find the exact break-even point. For most applications, the cheapest model is the one that minimises your total monthly bill given your input-to-output token ratio.
Frequently Asked Questions
Is o4-mini cheaper than Gemini 3.5 Flash? ▼
o4-mini is cheaper on input tokens at $1.10/1M vs $1.50/1M for Gemini 3.5 Flash — a 27% saving.
What is the context window of o4-mini vs Gemini 3.5 Flash? ▼
o4-mini has a 200,000-token context window. Gemini 3.5 Flash has a 1,000,000-token context window. Gemini 3.5 Flash supports the larger context, suitable for longer documents and agentic workflows.
Which model is better: o4-mini or Gemini 3.5 Flash? ▼
The best choice depends on your use case. For cost efficiency on input tokens, o4-mini is the cheaper option. For maximum context length, Gemini 3.5 Flash supports 1,000,000 tokens. Use the comparison table above to find the right fit for your workload.