Gemini 2.5 Flash vs GPT-5.5
2026 - Pricing, benchmarks, and use case comparison
Quick take
- •GPT-5.5 is open-weights - free to self-host with no API costs. Gemini 2.5 Flash requires paid API access.
- •Gemini 2.5 Flash has a 1M context window - 8x larger than GPT-5.5's 128K. Better for long documents and large codebases.
Specs comparison
| Gemini 2.5 Flash | GPT-5.5 | |
|---|---|---|
| Provider | Google DeepMind | OpenAI |
| Type | Closed source | Closed source |
| Context window | ✓1M | 128K |
| Input / 1M tokens | $0.075 | ✓Free (self-host) |
| Output / 1M tokens | $0.30 | Free (self-host) |
| Release date | 2025-05 | 2026-04 |
Benchmarks
| Benchmark | Gemini 2.5 Flash | GPT-5.5 |
|---|---|---|
| MMLU | ~89% | - |
| HumanEval | ~85% | - |
Scores sourced from official provider release posts.
Strengths
Gemini 2.5 Flash
- ✓Exceptional price-to-performance ratio
- ✓1M context at near-commodity pricing
- ✓Multimodal support at low cost
- ✓Fast inference latency
- ✓Strong summarization and classification
GPT-5.5
- ✓Improved instruction following over GPT-4o
- ✓Stronger long-context coherence
- ✓Better output consistency for agentic pipelines
- ✓GPT-5.5 Pro tier for reliability-critical workloads
- ✓Easier migration path than jumping from GPT-4o to GPT-5
Which should you choose?
Choose Gemini 2.5 Flash if you need...
- →High-volume, long-context tasks
- →Cost-sensitive production workloads
- →Document and media summarization
- →Retrieval-augmented pipelines
Choose GPT-5.5 if you need...
- →Production API integrations migrating from GPT-4o
- →Agentic workflows needing consistent structured output
- →Long-context document tasks
- →Teams deferring full GPT-5 migration costs