GLM-5.1 vs GPT-5.5 — LLM API Cost Comparison
Compare GLM-5.1 (Zhipu AI (GLM)) vs GPT-5.5 (OpenAI) 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
- $1.4/1M tokens
- Output
- $4.4/1M tokens
- Context
- 205K tokens
- Released
- 2026-03
Latest GLM flagship; improved reasoning over GLM-5
- Input
- $5/1M tokens
- Output
- $30/1M tokens
- Context
- 272K tokens
- Released
- 2026-04
Latest OpenAI frontier model; 272K context standard tier
Monthly Cost by Usage Tier (70% input / 30% output ratio)
| Usage | GLM-5.1 | GPT-5.5 | Cheaper by |
|---|---|---|---|
| Light (1M tokens) | $2.30 | $12.50 | GLM-5.1 (82%) |
| Moderate (10M tokens) | $23.00 | $125 | GLM-5.1 (82%) |
| Heavy (100M tokens) | $230 | $1,250 | GLM-5.1 (82%) |
| Very Heavy (1B tokens) | $2,300 | $12,500 | GLM-5.1 (82%) |
Frequently Asked Questions
Which is cheaper — GLM-5.1 or GPT-5.5?
For input tokens, GLM-5.1 is cheaper at $1.4/1M tokens — 3.6× less than $5/1M. For output tokens, GLM-5.1 wins at $4.4/1M vs $30/1M. At heavy workloads (100M tokens/month), the cost difference can be significant.
What is the context window difference between GLM-5.1 and GPT-5.5?
GLM-5.1 supports 204,800 tokens per request; GPT-5.5 supports 272,000 tokens. GPT-5.5 wins on context length, making it better for long documents, large codebases, or extended conversations without chunking.
When should I choose GLM-5.1 over GPT-5.5?
Choose GLM-5.1 (Zhipu AI (GLM)) if you prefer Zhipu AI (GLM)'s ecosystem, tooling, or reliability track record. Latest GLM flagship; improved reasoning over GLM-5. Choose GPT-5.5 (OpenAI) if Latest OpenAI frontier model; 272K context standard tier. 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 GLM-5.1 vs GPT-5.5?
At 700M input + 300M output tokens (1B total): GLM-5.1 costs $2300; GPT-5.5 costs $12500. The difference is $10200/billion tokens at this 70/30 input/output ratio.