Grok 4.20 vs o3
Grok 4.20 leads o3 on the Artificial Analysis Intelligence Index, 25.7 to 20.2, and Grok 4.20 costs 3.2x less per output token ($2.50 vs $8.00 per million). Updated October 21, 2026; 33 benchmarks have a result for both.
Grok 4.20 or o3: which to pick
Only Grok 4.20 has a coding score, 33.3 on the Vibe Coding Index; o3 has none, so the two cannot be ranked on coding.
Pick o3 for a lower cost per solved task ($0.571 against $0.72) and work measured by WeirdML or LegalBench (Vals AI), where it leads.
- Shared results
- 33
- Grok 4.20 only
- 22
- o3 only
- 69
- Like-for-like categories
- 8 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
Grok 4.20
Grok 4.20 leads, 25.7 against 20.2.
Same board, both measured
Reasoning
GPQA Diamond
Grok 4.20
Grok 4.20 leads, 88.6% against 84.1%.
Same board, both measured
Math
AIME
Grok 4.20
Grok 4.20 leads, 96.5% against 85.3%.
Same board, both measured
Knowledge
MMLU Pro
Grok 4.20
Grok 4.20 leads, 86.3% against 85.6%.
Same board, both measured
Web design
Design Arena: websites
Grok 4.20
Grok 4.20 leads, 1229 against 1036.
Same board, both measured
Long documents
Listed context window
Grok 4.20
Grok 4.20 takes 2M tokens against 200K.
Listed by OpenRouter
Everyday cost
1K input + 500 output tokens
Grok 4.20
Grok 4.20 $0.0025, o3 $0.0060 per turn.
List prices
Cost per solved task
One SWE-bench Verified task, solved
o3
Grok 4.20 $0.72, o3 $0.571.
Published attempt cost and pass rate
At a glance
- Coding index
- Grok 4.20 33.3 from 2 benchmarks, o3 not benchmarked.
- Widest category
- Web design, 18.8 points apart on average over 5 shared benchmarks.
- Widest single gap
- ARC-AGI-2: Grok 4.20 65.1% against o3 6.5%, 58.6 points apart on a 0 to 100 scale.
- Output price
- Grok 4.20 $2.50 against o3 $8.00 per million output tokens, 3.2x apart.
- Context window
- Grok 4.20 takes 2M tokens, o3 200K.
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 | o3 | Ties |
|---|---|---|---|---|
| Coding | 2 | 1 | ||
| Intelligence | 2 | 0 | ||
| Agentic work | 1 | 0 | ||
| Reasoning | 7 | 0 | ||
| Math | 1 | 0 | ||
| Knowledge | 2 | 5 | ||
| Web design | 5 | 0 | ||
| General | 3 | 4 | ||
| All shared boards | 23 | 10 |
CodingLike-for-likeSix of these boards feed the Vibe Coding Index21
| Benchmark | Grok 4.20 | o3 | Leader |
|---|---|---|---|
| Aider polyglot | Not measured | 81.3% | Only o3 measured |
| SWE-bench Verified | Not measured | 58.4% | Only o3 measured |
| SWE-bench Multimodal | Not measured | 36.0% | Only o3 measured |
| LiveCodeBench (Vals AI) | 84.3% | 83.9% | Grok 4.20 |
| 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 |
| LiveCodeBench (Artificial Analysis run) | Not measured | 80.8% | Only o3 measured |
| Terminal-Bench Hard (Artificial Analysis run) | 37.9% | 37.1% | Grok 4.20 |
| Terminal-Bench | 57.3% | Not measured | Only Grok 4.20 measured |
| GSO-Bench | Not measured | 8.8% | Only o3 measured |
| WeirdML | 52.3% | 52.4% | o3 |
| ALE-Bench | Not measured | 933.5 | Only o3 measured |
| LMArena Text: coding | Not measured | 1407 | Only o3 measured |
| LMArena Text: software and IT | Not measured | 1415 | Only o3 measured |
| SciCode | Not measured | 9.2% | Only o3 measured |
| Neither model has a result on the other 22 boards here | |||
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index20
| Benchmark | Grok 4.20 | o3 | Leader |
|---|---|---|---|
| AA Intelligence Index | 25.7 | 20.2 | Grok 4.20 |
| Epoch Capabilities Index | 152.1 | 146.7 | Grok 4.20 |
Agentic workLike-for-likePublic boards, shown as published, kept out of the index10
| Benchmark | Grok 4.20 | o3 | 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 | 1052 | 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% | 80.7% | Grok 4.20 |
| METR time horizons | Not measured | 65.4% | Only o3 measured |
| GDPval | Not measured | 30.8% | Only o3 measured |
| DeepResearch Bench | Not measured | 45.2% | Only o3 measured |
| OSWorld | Not measured | 23.0% | Only o3 measured |
| Vending-Bench 2 | $4,663 | Not measured | Only Grok 4.20 measured |
| Berkeley Function Calling Leaderboard (BFCL) | Not measured | 63.0% | Only o3 measured |
| BrowseComp-Plus | Not measured | 65.9% | Only o3 measured |
| Neither model has a result on the other 23 boards here | |||
ReasoningLike-for-likePublic boards, shown as published, kept out of the index70
| Benchmark | Grok 4.20 | o3 | Leader |
|---|---|---|---|
| GPQA Diamond | 88.6% | 84.1% | Grok 4.20 |
| MMMU Pro (Vals AI) | 83.5% | 80.4% | Grok 4.20 |
| GPQA Diamond (Artificial Analysis run) | 91.1% | 82.7% | Grok 4.20 |
| Humanity's Last Exam (Artificial Analysis run) | 34.5% | 20.1% | Grok 4.20 |
| GPQA Diamond (Epoch AI run) | Not measured | 81.8% | Only o3 measured |
| ARC-AGI | 89.5% | 60.8% | Grok 4.20 |
| ARC-AGI-2 | 65.1% | 6.5% | Grok 4.20 |
| SimpleBench | Not measured | 53.1% | Only o3 measured |
| Chess puzzles | Not measured | 37.0% | Only o3 measured |
| Mystery game puzzles | Not measured | 29.0% | Only o3 measured |
| VPCT | Not measured | 52.0% | Only o3 measured |
| LMArena Text: hard prompts | Not measured | 1402 | Only o3 measured |
| LMArena Text: expert | Not measured | 1402 | Only o3 measured |
| LMArena Text: hard prompts in English | Not measured | 1411 | Only o3 measured |
| LMArena Vision: diagrams | Not measured | 1220 | Only o3 measured |
| LMArena Vision: homework | Not measured | 1234 | Only o3 measured |
| Kagi LLM Benchmark | 75.0% | 67.6% | Grok 4.20 |
| Neither model has a result on the other 5 boards here | |||
MathLike-for-likePublic boards, shown as published, kept out of the index10
| Benchmark | Grok 4.20 | o3 | Leader |
|---|---|---|---|
| AIME | 96.5% | 85.3% | Grok 4.20 |
| MATH 500 (Vals AI) | Not measured | 94.6% | Only o3 measured |
| MGSM (Vals AI) | Not measured | 91.8% | Only o3 measured |
| AA Math Index | Not measured | 88.3 | Only o3 measured |
| AIME 2025 (Artificial Analysis run) | Not measured | 88.3% | Only o3 measured |
| OTIS Mock AIME | Not measured | 84.4% | Only o3 measured |
| FrontierMath, tiers 1 to 3 | Not measured | 33.3% | Only o3 measured |
| MATH level 5 | Not measured | 97.8% | Only o3 measured |
| LMArena Text: math | Not measured | 1426 | Only o3 measured |
| LMArena Text: mathematical work | Not measured | 1423 | Only o3 measured |
| Neither model has a result on the other 3 boards here | |||
KnowledgeLike-for-likePublic boards, shown as published, kept out of the index25
| Benchmark | Grok 4.20 | o3 | Leader |
|---|---|---|---|
| MMLU Pro | 86.3% | 85.6% | Grok 4.20 |
| LegalBench (Vals AI) | 77.7% | 83.8% | o3 |
| CaseLaw (Vals AI) | 54.4% | Not measured | Only Grok 4.20 measured |
| CorpFin (Vals AI) | 63.7% | 59.7% | Grok 4.20 |
| TaxEval (Vals AI) | 74.1% | 74.6% | o3 |
| MortgageTax (Vals AI) | 45.4% | 65.7% | o3 |
| MedQA (Vals AI) | 94.5% | 96.1% | o3 |
| MedCode (Vals AI) | 32.2% | 47.3% | o3 |
| MMLU Pro (Artificial Analysis run) | Not measured | 85.3% | Only o3 measured |
| SimpleQA Verified | Not measured | 49.4% | Only o3 measured |
| GeoBench | Not measured | 74.0% | Only o3 measured |
| LMArena Text: science | Not measured | 1429 | Only o3 measured |
| LMArena Text: medicine and healthcare | Not measured | 1448 | Only o3 measured |
| LMArena Text: legal and government | Not measured | 1428 | Only o3 measured |
| LMArena Text: business and finance | Not measured | 1393 | Only o3 measured |
| FACTS Benchmark Suite | Not measured | 44.4% | Only o3 measured |
| Neither model has a result on the other 2 boards here | |||
Web designLike-for-likePublic boards, shown as published, kept out of the index50
| Benchmark | Grok 4.20 | o3 | Leader |
|---|---|---|---|
| Design Arena: websites | 1229 | 1036 | Grok 4.20 |
| Design Arena: UI components | 1199 | 1017 | Grok 4.20 |
| Design Arena: game dev | 1192 | 1034 | Grok 4.20 |
| Design Arena: data viz | 1217 | 1200 | Grok 4.20 |
| Design Arena: 3D | 1193 | Not measured | Only Grok 4.20 measured |
| Design Arena: all code categories | 1221 | 1020 | Grok 4.20 |
| Design Arena: SVG | 1164 | Not measured | Only Grok 4.20 measured |
| Design Arena: ASCII art | 1174 | Not measured | Only Grok 4.20 measured |
| Neither model has a result on the other 1 board here | |||
GeneralLike-for-likePublic boards, shown as published, kept out of the index34
| Benchmark | Grok 4.20 | o3 | Leader |
|---|---|---|---|
| SAGE (Vals AI) | 38.2% | 41.8% | o3 |
| MedScribe (Vals AI) | 63.4% | 76.7% | o3 |
| Vals Multimodal Index | 39.1% | Not measured | Only Grok 4.20 measured |
| IFBench | 81.2% | 71.4% | Grok 4.20 |
| Long context reasoning (AA-LCR) | 69.0% | 74.7% | o3 |
| DTBench | 90.1% | 84.8% | Grok 4.20 |
| LMCA | 38.7% | 39.7% | o3 |
| Fiction.LiveBench | Not measured | 88.9% | Only o3 measured |
| Creative writing (Lech Mazur) | Not measured | 83.9% | Only o3 measured |
| CL-bench | 22.2% | 17.8% | Grok 4.20 |
| CL-bench Life | 11.9% | Not measured | Only Grok 4.20 measured |
| LMArena Text | Not measured | 1410 | Only o3 measured |
| LMArena Text: instruction following | Not measured | 1368 | Only o3 measured |
| LMArena Text: creative writing | Not measured | 1359 | Only o3 measured |
| LMArena Vision | Not measured | 1214 | Only o3 measured |
| LMArena Text: English | Not measured | 1417 | Only o3 measured |
| LMArena Text: non-English | Not measured | 1401 | Only o3 measured |
| LMArena Text: Chinese | Not measured | 1437 | Only o3 measured |
| LMArena Text: German | Not measured | 1420 | Only o3 measured |
| LMArena Text: Japanese | Not measured | 1403 | Only o3 measured |
| LMArena Text: Korean | Not measured | 1370 | Only o3 measured |
| LMArena Text: French | Not measured | 1430 | Only o3 measured |
| LMArena Text: Spanish | Not measured | 1395 | Only o3 measured |
| LMArena Text: Russian | Not measured | 1406 | Only o3 measured |
| LMArena Text: Polish | Not measured | 1438 | Only o3 measured |
| LMArena Text: multi-turn | Not measured | 1405 | Only o3 measured |
| LMArena Text: longer queries | Not measured | 1372 | Only o3 measured |
| LMArena Text: writing and language | Not measured | 1372 | Only o3 measured |
| LMArena Text: entertainment and media | Not measured | 1373 | Only o3 measured |
| LMArena Vision: English | Not measured | 1221 | Only o3 measured |
| LMArena Vision: Chinese | Not measured | 1237 | Only o3 measured |
| LMArena Vision: reading text | Not measured | 1218 | Only o3 measured |
| LMArena Vision: humor | Not measured | 1222 | Only o3 measured |
| LMArena Vision: captioning | Not measured | 1210 | Only o3 measured |
| LMArena Vision: recognizing things | Not measured | 1234 | Only o3 measured |
| LMArena Vision: creative writing | Not measured | 1201 | Only o3 measured |
| Neither model has a result on the other 10 boards here | |||
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
| Benchmark | Grok 4.20 | o3 | 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
Grok 4.20 costs less
Repository review
50K input + 3K output tokens
Grok 4.20 costs less
Agent loop
200K input + 10K output tokens
Grok 4.20 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 | OpenAI o3 |
|---|---|---|
| Maker | xAI | OpenAI |
| Weights | No public weights listed | No public weights listed |
| Released | March 31, 2026 | April 16, 2025 |
| Context window | 2M | 200K |
| Input $/Mtok | $1.25 | $2.00 |
| Output $/Mtok | $2.50 | $8.00 |
| Coding index | 33.3 | Not benchmarked |
| Independent measurements behind it | 2 | 0 |
| Cost per solved task | $0.72 | $0.571 |
| Source | OpenRouter listing | OpenRouter listing |
Questions
Is Grok 4.20 better than o3 for coding?
Only Grok 4.20 has a coding score, 33.3 on the Vibe Coding Index; o3 has none, so the two cannot be ranked on coding. Pick o3 for a lower cost per solved task ($0.571 against $0.72) and work measured by WeirdML or LegalBench (Vals AI), where it leads.
Which is cheaper, Grok 4.20 or o3?
Grok 4.20 costs $1.25 per million input tokens and $2.50 per million output tokens; o3 costs $2.00 and $8.00. Per solved SWE-bench Verified task, Grok 4.20 costs $0.72 and o3 $0.571.
Which has the bigger context window, Grok 4.20 or o3?
Grok 4.20, with 2M tokens against 200K.
How many benchmarks is the Grok 4.20 vs o3 comparison based on?
33 benchmarks have a result for both models as of October 21, 2026. Grok 4.20's coding index rests on 2 independent benchmarks and o3's on 0. Where only one model has a result, the page says so instead of naming a winner.