API cost decision in 10 seconds

🔥GLM 5.1 vs 🔥Gemini 3.1 Pro Preview

Pick GLM 5.1 for lower cost; pick Gemini 3.1 Pro Preview only if the larger context window matters more.

Pricing data updated:  Prices normalized to USD per 1M tokens Sample workload: 1M input + 500K output

Budget verdict

Pick GLM 5.1 for lower cost; pick Gemini 3.1 Pro Preview only if the larger context window matters more.

On the standard 1M input plus 500K output workload, GLM 5.1 is estimated at $2.52 vs $8 for Gemini 3.1 Pro Preview, saving $5.48 (68.5% lower).

Cost-first pickGLM 5.1
Context-first pickGemini 3.1 Pro Preview
Sample savings$5.4868.5%
10x traffic gap$54.8

Gemini 3.1 Pro Preview has more context, but GLM 5.1 saves $5.48 on the standard workload. At 10x that traffic, the same price gap is about $54.8. Use the calculator below to replace the sample workload with your own token volume.

Cheaper input GLM 5.1 $0.98 vs $2 / 1M

GLM 5.1 is $1.02 cheaper per 1M input tokens (51% lower; 2.04x difference).

Cheaper output GLM 5.1 $3.08 vs $12 / 1M

GLM 5.1 is $8.92 cheaper per 1M output tokens (74.3% lower; 3.9x difference).

Larger context Gemini 3.1 Pro Preview 202.75K vs 1.05M

Gemini 3.1 Pro Preview has 845.82K more context (5.17x larger).

Sample workload GLM 5.1 $2.52 vs $8

GLM 5.1 is $5.48 cheaper on the standard workload (68.5% lower).

Estimate your workload cost

Your Workload Cost

Prices are normalized to USD per 1M tokens.
GLM 5.1 Calculating… Estimated API cost
Gemini 3.1 Pro Preview Calculating… Estimated API cost
Cheaper for this workload Calculating… Difference: calculating…

This estimate uses normalized public API pricing per 1M tokens. It is a planning aid, not a billing quote. Verify provider pricing, limits, and terms before production use.

Quick Decision

Verdict

GLM 5.1 has the lower input price; GLM 5.1 has the lower output price; Gemini 3.1 Pro Preview offers the larger context window. For the 1M input plus 500K output sample, GLM 5.1 is cheaper for the standard workload.

For a 1M input token plus 500K output token workload, the estimated API cost is $2.52 for GLM 5.1 and $8 for Gemini 3.1 Pro Preview.

Best Fit

Choose GLM 5.1 when you care most about lower input-token price, and lower output-token price.

Choose Gemini 3.1 Pro Preview when you care most about larger context window.

Decision Notes
  • On the standard 1M input plus 500K output workload, GLM 5.1 is estimated at $2.52 vs $8 for Gemini 3.1 Pro Preview, saving $5.48 (68.5% lower).
  • GLM 5.1 is $5.48 cheaper on the standard workload (68.5% lower).
  • GLM 5.1 is $1.02 cheaper per 1M input tokens (51% lower; 2.04x difference).
  • GLM 5.1 is $8.92 cheaper per 1M output tokens (74.3% lower; 3.9x difference).
  • Gemini 3.1 Pro Preview has 845.82K more context (5.17x larger).
Head-to-Head Specs
Feature🔥GLM 5.1
(Z.ai)		🔥Gemini 3.1 Pro Preview
(Google)
Input Price
prompt tokens per 1M		$0.98$2
Completion Price
per 1M tokens		$3.08$12
Sample Workload Cost
1M input + 500K output		$2.52$8
Context Window202.75K1.05M
Release Date
Popularity Rank
current rank		#13#20

Use-Case Decision Matrix

Use caseBetter pickWhy
Budget-constrained productionGLM 5.1On the standard 1M input plus 500K output workload, GLM 5.1 is estimated at $2.52 vs $8 for Gemini 3.1 Pro Preview, saving $5.48 (68.5% lower).
High-volume input processingGLM 5.1Lower prompt-token price matters most when prompts, retrieved passages, or documents dominate the bill.
Long responses and chatbotsGLM 5.1Lower output-token price matters most when assistants generate many completion tokens.
RAG or long-document workGemini 3.1 Pro PreviewA larger context window leaves more room for retrieved passages, conversation history, or source files.

Related Alternatives

Same-provider lower-cost swaps
  • GLM 4.5 Air (free) can replace GLM 5.1 when lower sample workload cost matters most: $0.
  • GLM 4 32B can replace GLM 5.1 when lower sample workload cost matters most: $0.15.
  • GLM 4.7 Flash can replace GLM 5.1 when lower sample workload cost matters most: $0.26.
  • GLM 4.5 Air can replace GLM 5.1 when lower sample workload cost matters most: $0.55.
Larger context near this budget
  • Llama 4 Scout offers 10M context with $0.23 sample workload cost.
  • Grok 4.20 Multi-Agent offers 2M context with $5 sample workload cost.
  • Grok 4.20 offers 2M context with $2.5 sample workload cost.
  • GPT-5.4 offers 1.05M context with $10 sample workload cost.

Cheaper alternatives

Review low-cost models ranked by a standard 1M input plus 500K output workload.

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Larger context alternatives

Find models with larger context windows for RAG, long documents, and codebase review.

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Provider catalogs

Compare models within provider hubs before choosing a final API vendor.

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Z.ai catalog

Review all tracked Z.ai models before deciding whether this matchup is the right shortlist.

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Google catalog

Check other Google models with comparable pricing, context, or release timing.

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GLM 5.1

GLM-5.1 delivers a major leap in coding capability, with particularly significant gains in handling long-horizon tasks. Unlike previous models built around minute-level interactions, GLM-5.1 can work independently and continuously on...

Gemini 3.1 Pro Preview

Gemini 3.1 Pro Preview is Google’s frontier reasoning model, delivering enhanced software engineering performance, improved agentic reliability, and more efficient token usage across complex workflows. Building on the multimodal foundation...