LLM Reference

Gemini 2.5 Flash vs o3

Gemini 2.5 Flash (2025) and o3 (2025) are frontier reasoning models from Google DeepMind and OpenAI. Gemini 2.5 Flash ships a 1m-token context window, while o3 ships a 200k-token context window. On Google-Proof Q&A, o3 leads by 4.9 pts. On pricing, Gemini 2.5 Flash costs $0.30/1M input tokens versus $2/1M for the alternative. This comparison covers specs, pricing, API access, capabilities, benchmarks, input and output token costs, and production fit for coding and agent workloads.

Gemini 2.5 Flash is ~567% cheaper at $0.30/1M; pay for o3 only for coding workflow support.

Decision scorecard

Local evidence first
SignalGemini 2.5 Flasho3
Best formultimodal apps, tool-calling agents, and long-context analysisreasoning-heavy apps, multimodal apps, and tool-calling agents
Decision fitCoding, RAG, and AgentsCoding, RAG, and Agents
Context window1m200k
Cheapest output$2.50/1M tokens$8/1M tokens
Provider routes6 tracked3 tracked
Shared benchmarks6 sharedGoogle-Proof Q&A leader

Decision tradeoffs

Choose Gemini 2.5 Flash when...
  • Gemini 2.5 Flash has the larger context window for long prompts, retrieval packs, or transcript analysis.
  • Gemini 2.5 Flash has the lower cheapest tracked output price at $2.50/1M tokens.
  • Gemini 2.5 Flash has broader tracked provider coverage for fallback and route flexibility.
  • Local decision data tags Gemini 2.5 Flash for Coding, RAG, and Agents.
Choose o3 when...
  • o3 holds a shared-benchmark lead on Google-Proof Q&A, ahead by 4.9 points.
  • o3 uniquely exposes Reasoning in local model data.
  • Local decision data tags o3 for Coding, RAG, and Agents.

Monthly cost at traffic

Estimate token spend from the cheapest tracked input and output route or tier on this page.

Lower estimate Gemini 2.5 Flash

Gemini 2.5 Flash

$865

Cheapest tracked route/tier: Google AI Studio

o3

$3,600

Cheapest tracked route/tier: OpenAI API

Estimated monthly gap: $2,735. Batch, cache, alternate speed tiers, and negotiated pricing are excluded from this local estimate.

Switch friction

Gemini 2.5 Flash -> o3
  • Provider overlap exists on OpenRouter and Vercel AI Gateway; start route-level A/B tests there.
  • o3 is $5.50/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
  • o3 adds Reasoning in local capability data.
o3 -> Gemini 2.5 Flash
  • Provider overlap exists on OpenRouter and Vercel AI Gateway; start route-level A/B tests there.
  • Gemini 2.5 Flash is $5.50/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
  • Check replacement coverage for Reasoning before moving production traffic.

Specs

Specification
Released2025-06-172025-04-16
Context window1m200k
Parameters——
ArchitectureDecoder OnlyDecoder Only
LicenseProprietaryProprietary
OpennessProprietaryProprietary
WeightsNot releasedNot released
CodeUnknownUnknown
Commercial useCommercial use: conditionalCommercial use: conditional
Knowledge cutoff2025-012024-06

Pricing and availability

Pricing attributeGemini 2.5 Flasho3
Input price$0.30/1M tokens$2/1M tokens
Output price$2.50/1M tokens$8/1M tokens
Providers
Google AI StudioGCP Vertex AIReplicate APIOpenRouterVercel AI GatewayInceptron
OpenAI APIOpenRouterVercel AI Gateway

Capabilities

CapabilityGemini 2.5 Flasho3
VisionYesYes
MultimodalYesYes
ReasoningNoYes
JSON / Tool useYesYes
Structured outputsYesYes
Code executionYesYes
IDE integrationNoNo
Computer useNoNo
Parallel agentsNoNo

Benchmarks

BenchmarkGemini 2.5 Flasho3
Google-Proof Q&A82.887.7
LiveCodeBench76.285.5
Massive Multi-discipline Multimodal Understanding79.782.9
HumanEval90.196.7
Chatbot Arena1320.01412.0
Aider Polyglot55.181.3

Continue comparing

Model pages
Labs and families
Related comparisons

Popular comparisons for Gemini 2.5 Flash

Popular comparisons for o3

Last reviewed: 2026-06-29. Data sourced from public model cards and provider documentation.