CtrlAltDebrief

GLM 5.1 vs GPT-5.5

API pricing, context window and capabilities for GLM 5.1 and GPT-5.5, side by side. Prices are the cheapest serving route per 1M tokens, verified against LiteLLM and OpenRouter.

Verdict

computed from the published numbers

GLM 5.1 wins on price. GPT-5.5 wins on coding, on intelligence and on context window.

Price
GLM 5.1
Coding
GPT-5.5
Intelligence
GPT-5.5
Context window
GPT-5.5

Key takeaways

who wins on what, from the published numbers

GLM 5.1 wins

  • Cheaper input ($1.05 vs $5.00 /1M)
  • Cheaper output ($3.50 vs $30.00 /1M)

GPT-5.5 wins

  • Larger context window (203K vs 1.1M)
  • Supports vision
  • Supports structured output
  • Has web search
Cheaper overall
GLM 5.1
$1.05 + $3.50 /1M
Larger context
GPT-5.5
1.1M
More providers
Tied

Pricing & specs

cheapest serving route · per 1M tokens
GLM 5.1GPT-5.5
Input $/1M$1.05 best$5.00
Output $/1M$3.50 best$30.00
Context window203K 1.1M best
Max output128K 128K
Serving providers2 2
Released2026-04-07 2026-04-23

Benchmarks

Artificial Analysis indices, side by side
GLM 5.1GPT-5.5
Intelligence40.2 54.8 best
Coding55.8 74.9 best
GPQA Diamond87% 94% best
Output speed91 t/s best87 t/s
Latency (TTFT)10.49s best23.21s

Cost calculator

choose a serving route for each side
Input tokens / month
Output tokens / month
GLM 5.1
via OpenRouter
$8.75
GPT-5.5
via Azure
$55

Capabilities

feature support, side by side
FeatureGLM 5.1GPT-5.5
Vision—✓
Tool use✓✓
Reasoning✓✓
Audio——
Prompt caching✓✓
Structured output—✓
Web search—✓

Related comparisons

Frequently asked questions

Which is cheaper, GLM 5.1 or GPT-5.5?
GLM 5.1 is cheaper for input ($1.05 vs $5.00 per 1M tokens). GLM 5.1 is cheaper for output ($3.50 vs $30.00 per 1M tokens).
What is the context window difference between GLM 5.1 and GPT-5.5?
GLM 5.1 has a 203K-token context window and GPT-5.5 has 1.1M tokens, so GPT-5.5 can take a larger prompt.
How do GLM 5.1 and GPT-5.5 compare on benchmarks?
On the tracked Artificial Analysis indices, GPT-5.5 leads on coding, and GPT-5.5 leads on intelligence.
Pricing verified against LiteLLM + OpenRouter + provider pages · refreshed daily

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