GPT-5.5 vs DeepSeek V4 Flash — LLM API Cost Comparison
Compare GPT-5.5 (OpenAI) vs DeepSeek V4 Flash (DeepSeek) 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
- $0.14/1M tokens
- Output
- $0.28/1M tokens
- Context
- 1M tokens
- Released
- 2026-04
Default chat model (deepseek-chat alias); cache hit $0.0028/1M input
Monthly Cost by Usage Tier (70% input / 30% output ratio)
| Usage | GPT-5.5 | DeepSeek V4 Flash | Cheaper by |
|---|---|---|---|
| Light (1M tokens) | $12.50 | $0.182 | DeepSeek V4 Flash (99%) |
| Moderate (10M tokens) | $125 | $1.82 | DeepSeek V4 Flash (99%) |
| Heavy (100M tokens) | $1,250 | $18.20 | DeepSeek V4 Flash (99%) |
| Very Heavy (1B tokens) | $12,500 | $182 | DeepSeek V4 Flash (99%) |
Frequently Asked Questions
Which is cheaper — GPT-5.5 or DeepSeek V4 Flash?
For input tokens, DeepSeek V4 Flash is cheaper at $0.14/1M tokens — 35.7× less than $5/1M. For output tokens, DeepSeek V4 Flash wins at $0.28/1M 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 DeepSeek V4 Flash?
GPT-5.5 supports 272,000 tokens per request; DeepSeek V4 Flash supports 1,000,000 tokens. DeepSeek V4 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 DeepSeek V4 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 DeepSeek V4 Flash (DeepSeek) if Default chat model (deepseek-chat alias); cache hit $0.0028/1M input. 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 DeepSeek V4 Flash?
At 700M input + 300M output tokens (1B total): GPT-5.5 costs $12500; DeepSeek V4 Flash costs $182. The difference is $12318/billion tokens at this 70/30 input/output ratio.