Grok 4.20 vs Mercury 3
Mercury 3 costs 7.1x less per output token than Grok 4.20 ($0.35 vs $2.50 per million). Updated October 22, 2026; 5 benchmarks have a result for both.
Grok 4.20 or Mercury 3: which to pick
Only Grok 4.20 has a coding score, 33.3 on the Vibe Coding Index; Mercury 3 has none, so the two cannot be ranked on coding.
Pick Mercury 3 for output tokens 7.1x cheaper ($0.35 vs $2.50 per million) and work measured by Design Arena: websites or Design Arena: UI components, where it leads.
- Shared results
- 5
- Grok 4.20 only
- 50
- Mercury 3 only
- 0
- Like-for-like categories
- 1 of 9
Only benchmarks that tested both models count toward a pick; a result only one model has is shown but not compared.
Which one for your work
Each card is decided by one number both models carry. Where only one has it, the card says so and makes no call.
Coding
Vibe Coding Index, six public coding benchmarks
No call
Only Grok 4.20 has a coding score, so no call is made.
One side not measured
Intelligence
AA Intelligence Index
No call
Only Grok 4.20 has a AA Intelligence Index result, 25.7.
Directional only
Reasoning
GPQA Diamond
No call
Only Grok 4.20 has a GPQA Diamond result, 88.6%.
Directional only
Math
AIME
No call
Only Grok 4.20 has a AIME result, 96.5%.
Directional only
Knowledge
MMLU Pro
No call
Only Grok 4.20 has a MMLU Pro result, 86.3%.
Directional only
Web design
Design Arena: websites
Mercury 3
Mercury 3 leads, 1242 against 1229.
Same board, both measured
Long documents
Listed context window
Grok 4.20
Grok 4.20 takes 2M tokens against 1M.
Listed by OpenRouter
Everyday cost
1K input + 500 output tokens
Mercury 3
Grok 4.20 $0.0025, Mercury 3 $0.0003 per turn.
List prices
Cost per solved task
One SWE-bench Verified task, solved
No call
Only Grok 4.20 has the number, $0.72.
Directional only
At a glance
- Coding index
- Grok 4.20 33.3 from 2 benchmarks, Mercury 3 not benchmarked.
- Widest category
- Web design, 3.5 points apart on average over 5 shared benchmarks.
- Widest single gap
- Design Arena: UI components: Grok 4.20 1200 against Mercury 3 1255, 6.9 points apart on a 0 to 100 scale.
- Output price
- Grok 4.20 $2.50 against Mercury 3 $0.35 per million output tokens, 7.1x apart.
- Context window
- Grok 4.20 takes 2M tokens, Mercury 3 1M.
Benchmark by benchmark
First the score: boards each model leads, per category, where both have a result. Then every board, a category to a fold; bars are each result on a 0 to 100 scale, so compare the two in a row, not one row with another.
| Category | Grok 4.20 | Bars | Mercury 3 | Ties |
|---|---|---|---|---|
| Web design | 1 | 4 | ||
| All shared boards | 1 | 4 |
CodingDirectional onlySix of these boards feed the Vibe Coding Index8 boards, none shared
| Benchmark | Grok 4.20 | Mercury 3 | Leader |
|---|---|---|---|
| LiveCodeBench (Vals AI) | 84.3% | Not measured | Only Grok 4.20 measured |
| SWE-bench Verified (Vals AI) | 72.2% | Not measured | Only Grok 4.20 measured |
| Vibe Code Bench (Vals AI) | 4.1% | Not measured | Only Grok 4.20 measured |
| Code migration (Vals AI) | 0.3% | Not measured | Only Grok 4.20 measured |
| Terminal-Bench 2.1 (Vals AI) | 44.2% | Not measured | Only Grok 4.20 measured |
| Terminal-Bench Hard (Artificial Analysis run) | 37.9% | Not measured | Only Grok 4.20 measured |
| Terminal-Bench | 57.3% | Not measured | Only Grok 4.20 measured |
| WeirdML | 52.3% | Not measured | Only Grok 4.20 measured |
| Neither model has a result on the other 31 boards here | |||
IntelligenceDirectional onlyPublic boards, shown as published, kept out of the index2 boards, none shared
| Benchmark | Grok 4.20 | Mercury 3 | Leader |
|---|---|---|---|
| AA Intelligence Index | 25.7 | Not measured | Only Grok 4.20 measured |
| Epoch Capabilities Index | 152.1 | Not measured | Only Grok 4.20 measured |
Agentic workDirectional onlyPublic boards, shown as published, kept out of the index12 boards, none shared
| Benchmark | Grok 4.20 | Mercury 3 | Leader |
|---|---|---|---|
| Design Arena: agents building web apps | 1144 | Not measured | Only Grok 4.20 measured |
| Design Arena: agents building full-stack apps | 1054 | Not measured | Only Grok 4.20 measured |
| Design Arena: agents building mobile apps | 1090 | Not measured | Only Grok 4.20 measured |
| Design Arena: agents building Android apps | 1045 | Not measured | Only Grok 4.20 measured |
| Design Arena: agents building Godot games | 1089 | Not measured | Only Grok 4.20 measured |
| Design Arena: HTML slides | 1180 | Not measured | Only Grok 4.20 measured |
| Finance Agent (Vals AI) | 28.5% | Not measured | Only Grok 4.20 measured |
| Tax Agent Bench (Vals AI) | 7.0% | Not measured | Only Grok 4.20 measured |
| Legal Research Bench (Vals AI) | 13.9% | Not measured | Only Grok 4.20 measured |
| Excel Modeling Benchmark (Vals AI) | 11.7% | Not measured | Only Grok 4.20 measured |
| τ²-Bench Telecom | 93.0% | Not measured | Only Grok 4.20 measured |
| Vending-Bench 2 | $4,663 | Not measured | Only Grok 4.20 measured |
| Neither model has a result on the other 29 boards here | |||
ReasoningDirectional onlyPublic boards, shown as published, kept out of the index7 boards, none shared
| Benchmark | Grok 4.20 | Mercury 3 | Leader |
|---|---|---|---|
| GPQA Diamond | 88.6% | Not measured | Only Grok 4.20 measured |
| MMMU Pro (Vals AI) | 83.5% | Not measured | Only Grok 4.20 measured |
| GPQA Diamond (Artificial Analysis run) | 91.1% | Not measured | Only Grok 4.20 measured |
| Humanity's Last Exam (Artificial Analysis run) | 34.5% | Not measured | Only Grok 4.20 measured |
| ARC-AGI | 89.5% | Not measured | Only Grok 4.20 measured |
| ARC-AGI-2 | 65.1% | Not measured | Only Grok 4.20 measured |
| Kagi LLM Benchmark | 75.0% | Not measured | Only Grok 4.20 measured |
| Neither model has a result on the other 15 boards here | |||
MathDirectional onlyPublic boards, shown as published, kept out of the index1 board, none shared
| Benchmark | Grok 4.20 | Mercury 3 | Leader |
|---|---|---|---|
| AIME | 96.5% | Not measured | Only Grok 4.20 measured |
| Neither model has a result on the other 12 boards here | |||
KnowledgeDirectional onlyPublic boards, shown as published, kept out of the index8 boards, none shared
| Benchmark | Grok 4.20 | Mercury 3 | Leader |
|---|---|---|---|
| MMLU Pro | 86.3% | Not measured | Only Grok 4.20 measured |
| LegalBench (Vals AI) | 77.7% | Not measured | Only Grok 4.20 measured |
| CaseLaw (Vals AI) | 54.4% | Not measured | Only Grok 4.20 measured |
| CorpFin (Vals AI) | 63.7% | Not measured | Only Grok 4.20 measured |
| TaxEval (Vals AI) | 74.1% | Not measured | Only Grok 4.20 measured |
| MortgageTax (Vals AI) | 45.4% | Not measured | Only Grok 4.20 measured |
| MedQA (Vals AI) | 94.5% | Not measured | Only Grok 4.20 measured |
| MedCode (Vals AI) | 32.2% | Not measured | Only Grok 4.20 measured |
| Neither model has a result on the other 10 boards here | |||
Web designLike-for-likePublic boards, shown as published, kept out of the index14
| Benchmark | Grok 4.20 | Mercury 3 | Leader |
|---|---|---|---|
| Design Arena: websites | 1229 | 1242 | Mercury 3 |
| Design Arena: UI components | 1200 | 1255 | Mercury 3 |
| Design Arena: game dev | 1193 | 1225 | Mercury 3 |
| Design Arena: data viz | 1217 | 1192 | Grok 4.20 |
| Design Arena: 3D | 1193 | Not measured | Only Grok 4.20 measured |
| Design Arena: all code categories | 1221 | 1237 | Mercury 3 |
| Design Arena: SVG | 1165 | Not measured | Only Grok 4.20 measured |
| Design Arena: ASCII art | 1175 | Not measured | Only Grok 4.20 measured |
| Neither model has a result on the other 1 board here | |||
GeneralDirectional onlyPublic boards, shown as published, kept out of the index9 boards, none shared
| Benchmark | Grok 4.20 | Mercury 3 | Leader |
|---|---|---|---|
| SAGE (Vals AI) | 38.2% | Not measured | Only Grok 4.20 measured |
| MedScribe (Vals AI) | 63.4% | Not measured | Only Grok 4.20 measured |
| Vals Multimodal Index | 39.1% | Not measured | Only Grok 4.20 measured |
| IFBench | 81.2% | Not measured | Only Grok 4.20 measured |
| Long context reasoning (AA-LCR) | 69.0% | Not measured | Only Grok 4.20 measured |
| DTBench | 90.1% | Not measured | Only Grok 4.20 measured |
| LMCA | 38.7% | Not measured | Only Grok 4.20 measured |
| CL-bench | 22.2% | Not measured | Only Grok 4.20 measured |
| CL-bench Life | 11.9% | Not measured | Only Grok 4.20 measured |
| Neither model has a result on the other 37 boards here | |||
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
| Benchmark | Grok 4.20 | Mercury 3 | Leader |
|---|---|---|---|
| Neither model has a result on 5 boards here | |||
What each workload costs
Three fixed token mixes at each model's listed price, so per-token rates become a bill.
Chat turn
1K input + 500 output tokens
Mercury 3 costs less
Repository review
50K input + 3K output tokens
Mercury 3 costs less
Agent loop
200K input + 10K output tokens
Mercury 3 costs less
Listed OpenRouter rates, without cache or batch discounts. A workload that does not fit a model's context window would need splitting.
Specification differences
The leading value in a row is marked; a row with a missing value names no leader. Our two rows are marked in red.
| Specification | SpaceXAI Grok 4.20 | Inception Mercury 3 |
|---|---|---|
| Maker | xAI | Inception |
| Weights | No public weights listed | No public weights listed |
| Released | March 31, 2026 | October 16, 2026 |
| Context window | 2M | 1M |
| Input $/Mtok | $1.25 | $0.10 |
| Output $/Mtok | $2.50 | $0.35 |
| Coding index | 33.3 | Not benchmarked |
| Independent measurements behind it | 2 | 0 |
| Cost per solved task | $0.72 | Not computable |
| Source | OpenRouter listing | OpenRouter listing |
Questions
Is Grok 4.20 better than Mercury 3 for coding?
Only Grok 4.20 has a coding score, 33.3 on the Vibe Coding Index; Mercury 3 has none, so the two cannot be ranked on coding. Pick Mercury 3 for output tokens 7.1x cheaper ($0.35 vs $2.50 per million) and work measured by Design Arena: websites or Design Arena: UI components, where it leads.
Which is cheaper, Grok 4.20 or Mercury 3?
Grok 4.20 costs $1.25 per million input tokens and $2.50 per million output tokens; Mercury 3 costs $0.10 and $0.35. Cost per solved task is known for Grok 4.20 only.
Which has the bigger context window, Grok 4.20 or Mercury 3?
Grok 4.20, with 2M tokens against 1M.
How many benchmarks is the Grok 4.20 vs Mercury 3 comparison based on?
5 benchmarks have a result for both models as of October 22, 2026. Grok 4.20's coding index rests on 2 independent benchmarks and Mercury 3's on 0. Where only one model has a result, the page says so instead of naming a winner.