GLM-5.1 vs Gemini 3.5 Flash — LLM API Cost Comparison
Compare GLM-5.1 (Zhipu AI (GLM)) 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
- $1.4/1M tokens
- Output
- $4.4/1M tokens
- Context
- 205K tokens
- Released
- 2026-03
Latest GLM flagship; improved reasoning over GLM-5
- 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 | GLM-5.1 | Gemini 3.5 Flash | Cheaper by |
|---|---|---|---|
| Light (1M tokens) | $2.30 | $3.75 | GLM-5.1 (39%) |
| Moderate (10M tokens) | $23.00 | $37.50 | GLM-5.1 (39%) |
| Heavy (100M tokens) | $230 | $375 | GLM-5.1 (39%) |
| Very Heavy (1B tokens) | $2,300 | $3,750 | GLM-5.1 (39%) |
Frequently Asked Questions
Which is cheaper — GLM-5.1 or Gemini 3.5 Flash?
For input tokens, GLM-5.1 is cheaper at $1.4/1M tokens — 1.1× less than $1.5/1M. For output tokens, GLM-5.1 wins at $4.4/1M vs $9/1M. At heavy workloads (100M tokens/month), the cost difference can be significant.
What is the context window difference between GLM-5.1 and Gemini 3.5 Flash?
GLM-5.1 supports 204,800 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 GLM-5.1 over Gemini 3.5 Flash?
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 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 GLM-5.1 vs Gemini 3.5 Flash?
At 700M input + 300M output tokens (1B total): GLM-5.1 costs $2300; Gemini 3.5 Flash costs $3750. The difference is $1450/billion tokens at this 70/30 input/output ratio.