ZMIME
Comparison · 2 models · Updated Oct 4, 2026

Grok 4.20 (Reasoning) vs GLM-5.1

Grok 4.20 (Reasoning) comes out ahead, 68 to 57 on our weighted score, and it is the cheaper option too.

  1. Our pick

    xAI

    Grok 4.20 (Reasoning)

    Released Mar 9, 2026

    68/100
    • ECI152.0
    • Price$1.25 / $2.50
    • Context1M
    Full specs Remove Grok 4.20 (Reasoning)

  2. Z.ai (Zhipu)

    GLM-5.1

    Released Apr 7, 2026

    57/100
    • ECI149.9
    • Price$1.40 / $4.40
    • Context200K
    Full specs Remove GLM-5.1

  3. Add a model

    Make it a three-way comparison.

01 — Verdict

Grok 4.20 (Reasoning) is our pick

Grok 4.20 (Reasoning) is the better all-round choice, scoring 68/100 against GLM-5.1 (57). It leads on capability, price, inputs & features and context window. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.

  • CapabilityGrok 4.20 (Reasoning)Capabilities Index (ECI): Grok 4.20 (Reasoning) 152.0 · GLM-5.1 149.9
  • Lowest priceGrok 4.20 (Reasoning)Grok 4.20 (Reasoning) $1.56 · GLM-5.1 $2.15 per 1M tokens (3:1 blend)
  • Longest contextGrok 4.20 (Reasoning)Grok 4.20 (Reasoning) 1,000,000 · GLM-5.1 200,000 tokens
  • Widest inputsGrok 4.20 (Reasoning)Grok 4.20 (Reasoning): Text, Images, PDFs · GLM-5.1: Text
  • Self-hostingGLM-5.1Publishes downloadable weights
How the score is built
MeasureWeightGrok 4.20 (Reasoning)GLM-5.1
CapabilityCapabilities Index (ECI)50%8178
Price25%4134
Inputs & features15%8045
Context window10%6032
Overall100%68/10057/100
02 — Side by side

Every spec in one table

Highlighted cells lead their row. Dashes mean the data is not published.

Grok 4.20 (Reasoning) vs GLM-5.1 specifications side by side
SpecificationGrok 4.20 (Reasoning)xAIGLM-5.1Z.ai (Zhipu)
Capability
Capabilities Index (ECI)152.0 (best)149.9
ECI rank#41 of 148 (best)#51 of 148
GPQA DiamondGraduate-level science questions89.3%89.9% (best)
FrontierMath Tiers 1–3Research-level mathematics44.9% (best)36.8%
OTIS Mock AIME 2024–2025Competition mathematics92.2%93.3% (best)
SWE-bench VerifiedFixing real GitHub issues—74.2%
SimpleQA VerifiedShort factual questions30.2%34.0% (best)
Price per million tokens
Input$1.25 (best)$1.40
Output$2.50 (best)$4.40
Cached input$0.20 (best)$0.26
Blended (3:1)$1.56 (best)$2.15
Long-context rateOver 200K: $2.50 / $5.00Same rate
Price sourceOfficial xAI APIOfficial Z.AI API
Limits
Context window1,000,000 tokens (best)200,000 tokens
Max output30,000 tokens131,072 tokens (best)
Inputs and features
TextYesYes
ImagesYesNo
PDFsYesNo
AudioNoNo
VideoNoNo
ReasoningYesYes
Tool callingYesYes
Structured outputYesYes
Availability
WeightsProprietaryOpen
API model IDgrok-4.20-0309-reasoningglm-5.1
API providers1140 (best)
ReleasedMar 9, 2026Apr 7, 2026
Knowledge cutoff——
03 — Cost

What would a month cost?

Enter your expected volume in millions of tokens. List prices only; caching and batch discounts would lower these.

  • Grok 4.20 (Reasoning)$17.50
  • GLM-5.1$22.80
04 — Questions

Which should you choose?

Which is better: Grok 4.20 (Reasoning) or GLM-5.1?

Grok 4.20 (Reasoning) is the better all-round choice, scoring 68/100 against GLM-5.1 (57). It leads on capability, price, inputs & features and context window. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.

Which is cheaper, Grok 4.20 (Reasoning) or GLM-5.1?

Grok 4.20 (Reasoning) is cheaper at $1.25 input / $2.50 output per million tokens (official xAI API price). GLM-5.1 costs $1.40 input / $4.40 output per million tokens (official Z.AI API price). At a typical mix of three input tokens to one output token, that is $1.56 per million tokens for Grok 4.20 (Reasoning) versus $2.15 for GLM-5.1 (1.4× as much).

Which scores higher on benchmarks?

Grok 4.20 (Reasoning) scores higher on the Capabilities Index (ECI): Grok 4.20 (Reasoning) 152.0 (#41 of 148) and GLM-5.1 149.9 (#51 of 148). The confidence ranges of the top two overlap (149.3–154.4 vs 148.0–151.6), so treat the gap as small. On individual benchmarks: GPQA Diamond — GLM-5.1 89.9%, Grok 4.20 (Reasoning) 89.3%; FrontierMath Tiers 1–3 — Grok 4.20 (Reasoning) 44.9%, GLM-5.1 36.8%; OTIS Mock AIME 2024–2025 — GLM-5.1 93.3%, Grok 4.20 (Reasoning) 92.2%; SimpleQA Verified — GLM-5.1 34.0%, Grok 4.20 (Reasoning) 30.2%.

Which is better for coding?

There are no published SWE-bench Verified results for Grok 4.20 (Reasoning) yet, so there is no like-for-like coding score. On overall capability, Grok 4.20 (Reasoning) leads, which tends to carry over to coding, but test on your own codebase. Both support tool calling for agent workflows.

Which has the bigger context window?

Grok 4.20 (Reasoning) has the largest context window at 1,000,000 tokens, against 200,000 for GLM-5.1. Maximum output per response: Grok 4.20 (Reasoning) up to 30,000, GLM-5.1 up to 131,072 tokens.

Which can read images, PDFs, audio or video?

Grok 4.20 (Reasoning) accepts text, images and PDFs; GLM-5.1 accepts text. Grok 4.20 (Reasoning) handles the widest range of inputs.

Are any of these open source?

GLM-5.1 publishes its weights and can be self-hosted; Grok 4.20 (Reasoning) is proprietary.

Which is newer?

GLM-5.1 is the newest, released Apr 7, 2026. Grok 4.20 (Reasoning) came out Mar 9, 2026.

How do you decide the winner?

Each model gets a 0–100 score on capability (50%, independent benchmark results); price (25%, blended price per million tokens (3 input : 1 output), log scale); inputs & features (15%, image, PDF, audio and video input, tool calling, structured output and reasoning); context window (10%, maximum tokens per request, log scale). Dimensions missing for any model are dropped and the remaining weights rescaled, so every model is judged on the same evidence. Specs and prices come from public model listings and the labs’ own API pages; capability scores come from independent benchmark runs. Data updated Oct 4, 2026.

05 — Keep comparing

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