GPT-5.5 vs Gemini 3.5 Flash — LLM API Cost Comparison
Compare GPT-5.5 (OpenAI) vs Gemini 3.5 Flash (Google) on cost per million tokens, context window, and monthly spend.
Prices verified 2026-05-23 · Pricing may change — use the calculator for current estimates
- Input
- $5/1M tokens
- Output
- $30/1M tokens
- Context
- 272K tokens
- Released
- 2026-04
Latest OpenAI frontier model; 272K context standard tier
- Input
- $1.5/1M tokens
- Output
- $9/1M tokens
- Context
- 1M tokens
- Released
- 2026-05
Latest Gemini; frontier intelligence + superior search & grounding
Monthly Cost by Usage Tier (70% input / 30% output ratio)
| Usage | GPT-5.5 | Gemini 3.5 Flash | Cheaper by |
|---|---|---|---|
| Light (1M tokens) | $12.50 | $3.75 | Gemini 3.5 Flash (70%) |
| Moderate (10M tokens) | $125 | $37.50 | Gemini 3.5 Flash (70%) |
| Heavy (100M tokens) | $1,250 | $375 | Gemini 3.5 Flash (70%) |
| Very Heavy (1B tokens) | $12,500 | $3,750 | Gemini 3.5 Flash (70%) |
Frequently Asked Questions
Which is cheaper — GPT-5.5 or Gemini 3.5 Flash?
For input tokens, Gemini 3.5 Flash is cheaper at $1.5/1M tokens — 3.3× less than $5/1M. For output tokens, Gemini 3.5 Flash wins at $9/1M vs $30/1M. At heavy workloads (100M tokens/month), the cost difference can be significant.
What is the context window difference between GPT-5.5 and Gemini 3.5 Flash?
GPT-5.5 supports 272,000 tokens per request; Gemini 3.5 Flash supports 1,000,000 tokens. Gemini 3.5 Flash wins on context length, making it better for long documents, large codebases, or extended conversations without chunking.
When should I choose GPT-5.5 over Gemini 3.5 Flash?
Choose GPT-5.5 (OpenAI) if you prefer OpenAI's ecosystem, tooling, or reliability track record. Latest OpenAI frontier model; 272K context standard tier. Choose Gemini 3.5 Flash (Google) if Latest Gemini; frontier intelligence + superior search & grounding. the price/performance fits your workload better. Use this calculator to find the break-even point for your exact token volume.
How much does 1 billion tokens cost on GPT-5.5 vs Gemini 3.5 Flash?
At 700M input + 300M output tokens (1B total): GPT-5.5 costs $12500; Gemini 3.5 Flash costs $3750. The difference is $8750/billion tokens at this 70/30 input/output ratio.