GPT-5.5 Pro vs GLM-5.1
Detailed pricing comparison and cost analysis.
Updated September 2026
Cost Simulator
| Feature | GPT-5.5 Pro | GLM-5.1 |
|---|---|---|
| Provider | OpenAI | Zhipu AI |
| Input Price (1M) | $30.00 | $1.40 |
| Output Price (1M) | $180.00 | $4.40 |
| Context Window | 1,000,000 | 1,000,000 |
Verdict
GPT-5.5 Pro costs $30.00 per 1M input tokens and $180.00 per 1M output tokens. GLM-5.1 costs $1.40 per 1M input tokens and $4.40 per 1M output tokens. GLM-5.1 is 95% cheaper on input tokens than GPT-5.5 Pro. For output tokens, GLM-5.1 is the more affordable option at $4.40/1M vs $180.00.
On context window, GPT-5.5 Pro supports 1,000,000 tokens — meaning it can fit more conversation history, documents, or code in a single request. This matters for RAG pipelines, long document analysis, and agentic workflows where context builds up over many turns.
When to choose GPT-5.5 Pro
- ✓ You are already integrated with OpenAI
When to choose GLM-5.1
- ✓ You need the lowest input token cost ($ 1.40/1M)
- ✓ Your workload is output-heavy — GLM-5.1 generates text cheaper
- ✓ You are already integrated with Zhipu AI
Use the calculator above to simulate your specific workload and find the exact break-even point. For most applications, the cheapest model is the one that minimises your total monthly bill given your input-to-output token ratio.
Frequently Asked Questions
Is GPT-5.5 Pro cheaper than GLM-5.1? ▼
GLM-5.1 is cheaper on input tokens at $1.40/1M vs $30.00/1M for GPT-5.5 Pro — a 95% saving.
What is the context window of GPT-5.5 Pro vs GLM-5.1? ▼
GPT-5.5 Pro has a 1,000,000-token context window. GLM-5.1 has a 1,000,000-token context window. GPT-5.5 Pro supports the larger context, suitable for longer documents and agentic workflows.
Which model is better: GPT-5.5 Pro or GLM-5.1? ▼
The best choice depends on your use case. For cost efficiency on input tokens, GLM-5.1 is the cheaper option. For maximum context length, GPT-5.5 Pro supports 1,000,000 tokens. Use the comparison table above to find the right fit for your workload.