API cost decision in 10 seconds

🔥Grok 4.1 Fast vs 🔥GLM 5.1

Pick Grok 4.1 Fast when budget and context both matter.

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

Budget verdict

Pick Grok 4.1 Fast when budget and context both matter.

On the standard 1M input plus 500K output workload, Grok 4.1 Fast is estimated at $0.45 vs $2.52 for GLM 5.1, saving $2.07 (82.1% lower).

Cost-first pickGrok 4.1 Fast
Context-first pickGrok 4.1 Fast
Sample savings$2.0782.1%
10x traffic gap$20.7

Grok 4.1 Fast is cheaper on the standard workload and also has the larger context window. At 10x that traffic, the same price gap is about $20.7. Use the calculator below to replace the sample workload with your own token volume.

Cheaper input Grok 4.1 Fast $0.2 vs $0.98 / 1M

Grok 4.1 Fast is $0.78 cheaper per 1M input tokens (79.6% lower; 4.9x difference).

Cheaper output Grok 4.1 Fast $0.5 vs $3.08 / 1M

Grok 4.1 Fast is $2.58 cheaper per 1M output tokens (83.8% lower; 6.16x difference).

Larger context Grok 4.1 Fast 2M vs 202.75K

Grok 4.1 Fast has 1.8M more context (9.86x larger).

Sample workload Grok 4.1 Fast $0.45 vs $2.52

Grok 4.1 Fast is $2.07 cheaper on the standard workload (82.1% lower).

Estimate your workload cost

Your Workload Cost

Prices are normalized to USD per 1M tokens.
Grok 4.1 Fast Calculating… Estimated API cost
GLM 5.1 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

Grok 4.1 Fast has the lower input price; Grok 4.1 Fast has the lower output price; Grok 4.1 Fast offers the larger context window. For the 1M input plus 500K output sample, Grok 4.1 Fast is cheaper for the standard workload.

For a 1M input token plus 500K output token workload, the estimated API cost is $0.45 for Grok 4.1 Fast and $2.52 for GLM 5.1.

Best Fit

Choose Grok 4.1 Fast when you care most about lower input-token price, lower output-token price, and larger context window.

Choose GLM 5.1 when its provider, model quality, latency, or availability is more important than the numeric price/context winner.

Decision Notes
  • On the standard 1M input plus 500K output workload, Grok 4.1 Fast is estimated at $0.45 vs $2.52 for GLM 5.1, saving $2.07 (82.1% lower).
  • Grok 4.1 Fast is $2.07 cheaper on the standard workload (82.1% lower).
  • Grok 4.1 Fast is $0.78 cheaper per 1M input tokens (79.6% lower; 4.9x difference).
  • Grok 4.1 Fast is $2.58 cheaper per 1M output tokens (83.8% lower; 6.16x difference).
  • Grok 4.1 Fast has 1.8M more context (9.86x larger).
Head-to-Head Specs
Feature🔥Grok 4.1 Fast
(xAI)		🔥GLM 5.1
(Z.ai)
Input Price
prompt tokens per 1M		$0.2$0.98
Completion Price
per 1M tokens		$0.5$3.08
Sample Workload Cost
1M input + 500K output		$0.45$2.52
Context Window2M202.75K
Release Date
Popularity Rank
current rank		#18#20

Use-Case Decision Matrix

Use caseBetter pickWhy
Budget-constrained productionGrok 4.1 FastOn the standard 1M input plus 500K output workload, Grok 4.1 Fast is estimated at $0.45 vs $2.52 for GLM 5.1, saving $2.07 (82.1% lower).
High-volume input processingGrok 4.1 FastLower prompt-token price matters most when prompts, retrieved passages, or documents dominate the bill.
Long responses and chatbotsGrok 4.1 FastLower output-token price matters most when assistants generate many completion tokens.
RAG or long-document workGrok 4.1 FastA 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
  • No larger-context model is currently tracked within a close sample-cost band.

Cheaper alternatives

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

Open cheapest models

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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xAI catalog

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

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Z.ai catalog

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

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