o3 vs Gemini 2.5 Flash
Pricing, context window, and benchmark comparison · Last updated April 2026
Gemini 2.5 Flash is cheaper than o3 at $0.30/1M/1M vs $2.00/1M/1M input tokens — a 6.7x cost difference. o3 scores higher on quality benchmarks (ELO 1395). Choose Gemini 2.5 Flash for cost-sensitive workloads; choose o3 for maximum quality.
Which is cheaper: o3 or Gemini 2.5 Flash?
Gemini 2.5 Flash is the cheaper option at $0.30/1M per 1M input tokens, compared to $2.00/1M for o3. That is a 6.7x cost difference on input tokens. Output pricing follows a similar pattern: o3 charges $8.00/1M/1M vs $2.50/1M/1M for Gemini 2.5 Flash.
Which has better quality: o3 or Gemini 2.5 Flash?
Based on LMSYS Chatbot Arena rankings, o3 achieves a higher ELO score (1395 vs 1340), suggesting stronger performance on open-ended tasks. o3 excels at top-tier reasoning on math, science, and agentic tasks. Gemini 2.5 Flash is known for excellent price-performance at flash tier.
Which should you choose: o3 or Gemini 2.5 Flash?
- → Top-tier reasoning on math, science, and agentic tasks
- → 87% cheaper than original o1 at the same capability tier
- → 200K context window
- → Excellent price-performance at Flash tier
- → 1M token context window
- → Native multimodal
Frequently Asked Questions
Which is cheaper: o3 or Gemini 2.5 Flash?
Gemini 2.5 Flash is cheaper at $0.30/1M per 1M input tokens, making it 6.7x more affordable.
Which has better quality: o3 or Gemini 2.5 Flash?
o3 scores higher on the LMSYS Chatbot Arena with an ELO of 1395, suggesting better overall quality for most tasks.
Which has a larger context window: o3 or Gemini 2.5 Flash?
Gemini 2.5 Flash has a larger context window at 1000K tokens.
Should I choose o3 or Gemini 2.5 Flash?
Choose Gemini 2.5 Flash if cost is the priority. Choose o3 if benchmark quality is most important. Consider your specific use case: o3 is best for reasoning and math, while Gemini 2.5 Flash excels at fast-response and low-cost.
Is o3 or Gemini 2.5 Flash open source?
o3 is proprietary. Gemini 2.5 Flash is proprietary.