GPT-5 Nano vs Grok 4.20
Grok 4.20 leads GPT-5 Nano on the Artificial Analysis Intelligence Index, 25.7 to 13.0, and GPT-5 Nano costs 6.3x less per output token ($0.40 vs $2.50 per million). Updated October 22, 2026; 34 benchmarks have a result for both.
GPT-5 Nano or Grok 4.20: which to pick
Only Grok 4.20 has a coding score, 33.3 on the Vibe Coding Index; GPT-5 Nano has none, so the two cannot be ranked on coding.
Pick GPT-5 Nano for output tokens 6.3x cheaper ($0.40 vs $2.50 per million) and a lower cost per solved task ($0.109 against $0.72).
- Shared results
- 34
- GPT-5 Nano only
- 53
- Grok 4.20 only
- 21
- 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 13.0.
Same board, both measured
Reasoning
GPQA Diamond
Grok 4.20
Grok 4.20 leads, 88.6% against 63.4%.
Same board, both measured
Math
AIME
Grok 4.20
Grok 4.20 leads, 96.5% against 81.2%.
Same board, both measured
Knowledge
MMLU Pro
Grok 4.20
Grok 4.20 leads, 86.3% against 76.1%.
Same board, both measured
Web design
Design Arena: websites
Grok 4.20
Grok 4.20 leads, 1229 against 1101.
Same board, both measured
Long documents
Listed context window
Grok 4.20
Grok 4.20 takes 2M tokens against 400K.
Listed by OpenRouter
Everyday cost
1K input + 500 output tokens
GPT-5 Nano
GPT-5 Nano $0.0003, Grok 4.20 $0.0025 per turn.
List prices
Cost per solved task
One SWE-bench Verified task, solved
GPT-5 Nano
GPT-5 Nano $0.109, Grok 4.20 $0.72.
Published attempt cost and pass rate
At a glance
- Coding index
- GPT-5 Nano not benchmarked, Grok 4.20 33.3 from 2 benchmarks.
- Widest category
- Agentic work, 56.4 points apart on average over 1 shared benchmark.
- Widest single gap
- ARC-AGI: GPT-5 Nano 20.7% against Grok 4.20 89.5%, 68.8 points apart on a 0 to 100 scale.
- Output price
- GPT-5 Nano $0.40 against Grok 4.20 $2.50 per million output tokens, 6.3x apart.
- Context window
- GPT-5 Nano takes 400K tokens, Grok 4.20 2M.
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 | GPT-5 Nano | Bars | Grok 4.20 | Ties |
|---|---|---|---|---|
| Coding | 0 | 4 | ||
| Intelligence | 0 | 2 | ||
| Agentic work | 0 | 1 | ||
| Reasoning | 0 | 7 | ||
| Math | 0 | 1 | ||
| Knowledge | 1 | 6 | ||
| Web design | 0 | 6 | ||
| General | 1 | 5 | ||
| All shared boards | 2 | 32 |
CodingLike-for-likeSix of these boards feed the Vibe Coding Index04
| Benchmark | GPT-5 Nano | Grok 4.20 | Leader |
|---|---|---|---|
| SWE-bench Verified | 34.8% | Not measured | Only GPT-5 Nano measured |
| LiveCodeBench (Vals AI) | 70.2% | 84.3% | Grok 4.20 |
| SWE-bench Verified (Vals AI) | Not measured | 72.2% | Only Grok 4.20 measured |
| Vibe Code Bench (Vals AI) | Not measured | 4.1% | Only Grok 4.20 measured |
| Code migration (Vals AI) | Not measured | 0.3% | Only Grok 4.20 measured |
| Terminal-Bench 2.1 (Vals AI) | Not measured | 44.2% | Only Grok 4.20 measured |
| LiveCodeBench (Artificial Analysis run) | 78.9% | Not measured | Only GPT-5 Nano measured |
| Terminal-Bench Hard (Artificial Analysis run) | 17.4% | 37.9% | Grok 4.20 |
| Terminal-Bench | 21.8% | 57.3% | Grok 4.20 |
| WeirdML | 38.1% | 52.3% | Grok 4.20 |
| LMArena Text: coding | 1351 | Not measured | Only GPT-5 Nano measured |
| LMArena Text: software and IT | 1345 | Not measured | Only GPT-5 Nano measured |
| Neither model has a result on the other 27 boards here | |||
IntelligenceLike-for-likePublic boards, shown as published, kept out of the index02
| Benchmark | GPT-5 Nano | Grok 4.20 | Leader |
|---|---|---|---|
| AA Intelligence Index | 13.0 | 25.7 | Grok 4.20 |
| Epoch Capabilities Index | 139.2 | 152.1 | Grok 4.20 |
Agentic workLike-for-likePublic boards, shown as published, kept out of the index01
| Benchmark | GPT-5 Nano | Grok 4.20 | Leader |
|---|---|---|---|
| Design Arena: agents building web apps | Not measured | 1144 | Only Grok 4.20 measured |
| Design Arena: agents building full-stack apps | Not measured | 1054 | Only Grok 4.20 measured |
| Design Arena: agents building mobile apps | Not measured | 1090 | Only Grok 4.20 measured |
| Design Arena: agents building Android apps | Not measured | 1045 | Only Grok 4.20 measured |
| Design Arena: agents building Godot games | Not measured | 1089 | Only Grok 4.20 measured |
| Design Arena: HTML slides | Not measured | 1180 | Only Grok 4.20 measured |
| Finance Agent (Vals AI) | Not measured | 28.5% | Only Grok 4.20 measured |
| Tax Agent Bench (Vals AI) | Not measured | 7.0% | Only Grok 4.20 measured |
| Legal Research Bench (Vals AI) | Not measured | 13.9% | Only Grok 4.20 measured |
| Excel Modeling Benchmark (Vals AI) | Not measured | 11.7% | Only Grok 4.20 measured |
| τ²-Bench Telecom | 36.5% | 93.0% | Grok 4.20 |
| Vending-Bench 2 | Not measured | $4,663 | Only Grok 4.20 measured |
| Berkeley Function Calling Leaderboard (BFCL) | 51.4% | Not measured | Only GPT-5 Nano measured |
| Neither model has a result on the other 28 boards here | |||
ReasoningLike-for-likePublic boards, shown as published, kept out of the index07
| Benchmark | GPT-5 Nano | Grok 4.20 | Leader |
|---|---|---|---|
| GPQA Diamond | 63.4% | 88.6% | Grok 4.20 |
| MMMU Pro (Vals AI) | 70.9% | 83.5% | Grok 4.20 |
| GPQA Diamond (Artificial Analysis run) | 67.6% | 91.1% | Grok 4.20 |
| Humanity's Last Exam (Artificial Analysis run) | 9.5% | 34.5% | Grok 4.20 |
| GPQA Diamond (Epoch AI run) | 69.4% | Not measured | Only GPT-5 Nano measured |
| ARC-AGI | 20.7% | 89.5% | Grok 4.20 |
| ARC-AGI-2 | 2.6% | 65.1% | Grok 4.20 |
| Chess puzzles | 22.0% | Not measured | Only GPT-5 Nano measured |
| Mystery game puzzles | 9.0% | Not measured | Only GPT-5 Nano measured |
| VPCT | 37.2% | Not measured | Only GPT-5 Nano measured |
| LMArena Text: hard prompts | 1328 | Not measured | Only GPT-5 Nano measured |
| LMArena Text: expert | 1321 | Not measured | Only GPT-5 Nano measured |
| LMArena Text: hard prompts in English | 1338 | Not measured | Only GPT-5 Nano measured |
| LMArena Vision: diagrams | 1141 | Not measured | Only GPT-5 Nano measured |
| LMArena Vision: homework | 1157 | Not measured | Only GPT-5 Nano measured |
| Kagi LLM Benchmark | 62.2% | 75.0% | Grok 4.20 |
| Neither model has a result on the other 6 boards here | |||
MathLike-for-likePublic boards, shown as published, kept out of the index01
| Benchmark | GPT-5 Nano | Grok 4.20 | Leader |
|---|---|---|---|
| AIME | 81.2% | 96.5% | Grok 4.20 |
| MATH 500 (Vals AI) | 93.8% | Not measured | Only GPT-5 Nano measured |
| MGSM (Vals AI) | 89.3% | Not measured | Only GPT-5 Nano measured |
| AA Math Index | 83.7 | Not measured | Only GPT-5 Nano measured |
| AIME 2025 (Artificial Analysis run) | 83.7% | Not measured | Only GPT-5 Nano measured |
| OTIS Mock AIME | 81.1% | Not measured | Only GPT-5 Nano measured |
| FrontierMath, tiers 1 to 3 | 20.0% | Not measured | Only GPT-5 Nano measured |
| FrontierMath, tier 4 | 2.4% | Not measured | Only GPT-5 Nano measured |
| ProofBench | 12.0% | Not measured | Only GPT-5 Nano measured |
| MATH level 5 | 95.2% | Not measured | Only GPT-5 Nano measured |
| LMArena Text: math | 1317 | Not measured | Only GPT-5 Nano measured |
| LMArena Text: mathematical work | 1326 | Not measured | Only GPT-5 Nano measured |
| Neither model has a result on the other 1 board here | |||
KnowledgeLike-for-likePublic boards, shown as published, kept out of the index16
| Benchmark | GPT-5 Nano | Grok 4.20 | Leader |
|---|---|---|---|
| MMLU Pro | 76.1% | 86.3% | Grok 4.20 |
| LegalBench (Vals AI) | 50.1% | 77.7% | Grok 4.20 |
| CaseLaw (Vals AI) | 52.6% | 54.4% | Grok 4.20 |
| CorpFin (Vals AI) | Not measured | 63.7% | Only Grok 4.20 measured |
| TaxEval (Vals AI) | 67.4% | 74.1% | Grok 4.20 |
| MortgageTax (Vals AI) | 53.6% | 45.4% | GPT-5 Nano |
| MedQA (Vals AI) | 93.3% | 94.5% | Grok 4.20 |
| MedCode (Vals AI) | 30.4% | 32.2% | Grok 4.20 |
| MMLU Pro (Artificial Analysis run) | 78.0% | Not measured | Only GPT-5 Nano measured |
| SimpleQA Verified | 11.7% | Not measured | Only GPT-5 Nano measured |
| LMArena Text: science | 1318 | Not measured | Only GPT-5 Nano measured |
| LMArena Text: medicine and healthcare | 1335 | Not measured | Only GPT-5 Nano measured |
| LMArena Text: legal and government | 1298 | Not measured | Only GPT-5 Nano measured |
| LMArena Text: business and finance | 1311 | Not measured | Only GPT-5 Nano measured |
| Neither model has a result on the other 4 boards here | |||
Web designLike-for-likePublic boards, shown as published, kept out of the index06
| Benchmark | GPT-5 Nano | Grok 4.20 | Leader |
|---|---|---|---|
| Design Arena: websites | 1101 | 1229 | Grok 4.20 |
| Design Arena: UI components | 1064 | 1200 | Grok 4.20 |
| Design Arena: game dev | 1044 | 1193 | Grok 4.20 |
| Design Arena: data viz | 1056 | 1217 | Grok 4.20 |
| Design Arena: 3D | 965 | 1193 | Grok 4.20 |
| Design Arena: all code categories | 1084 | 1221 | Grok 4.20 |
| Design Arena: SVG | Not measured | 1165 | Only Grok 4.20 measured |
| Design Arena: ASCII art | Not measured | 1175 | 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 index15
| Benchmark | GPT-5 Nano | Grok 4.20 | Leader |
|---|---|---|---|
| SAGE (Vals AI) | 30.4% | 38.2% | Grok 4.20 |
| MedScribe (Vals AI) | 72.9% | 63.4% | GPT-5 Nano |
| Vals Multimodal Index | Not measured | 39.1% | Only Grok 4.20 measured |
| IFBench | 67.6% | 81.2% | Grok 4.20 |
| Long context reasoning (AA-LCR) | 45.0% | 69.0% | Grok 4.20 |
| DTBench | 62.7% | 90.1% | Grok 4.20 |
| LMCA | 7.9% | 38.7% | Grok 4.20 |
| Fiction.LiveBench | 44.4% | Not measured | Only GPT-5 Nano measured |
| CL-bench | Not measured | 22.2% | Only Grok 4.20 measured |
| CL-bench Life | Not measured | 11.9% | Only Grok 4.20 measured |
| LMArena Text | 1320 | Not measured | Only GPT-5 Nano measured |
| LMArena Text: instruction following | 1306 | Not measured | Only GPT-5 Nano measured |
| LMArena Text: creative writing | 1249 | Not measured | Only GPT-5 Nano measured |
| LMArena Vision | 1159 | Not measured | Only GPT-5 Nano measured |
| LMArena Text: English | 1321 | Not measured | Only GPT-5 Nano measured |
| LMArena Text: non-English | 1313 | Not measured | Only GPT-5 Nano measured |
| LMArena Text: Chinese | 1356 | Not measured | Only GPT-5 Nano measured |
| LMArena Text: German | 1327 | Not measured | Only GPT-5 Nano measured |
| LMArena Text: Japanese | 1227 | Not measured | Only GPT-5 Nano measured |
| LMArena Text: Korean | 1269 | Not measured | Only GPT-5 Nano measured |
| LMArena Text: Spanish | 1360 | Not measured | Only GPT-5 Nano measured |
| LMArena Text: Russian | 1296 | Not measured | Only GPT-5 Nano measured |
| LMArena Text: Polish | 1314 | Not measured | Only GPT-5 Nano measured |
| LMArena Text: multi-turn | 1311 | Not measured | Only GPT-5 Nano measured |
| LMArena Text: longer queries | 1312 | Not measured | Only GPT-5 Nano measured |
| LMArena Text: writing and language | 1283 | Not measured | Only GPT-5 Nano measured |
| LMArena Text: entertainment and media | 1268 | Not measured | Only GPT-5 Nano measured |
| LMArena Vision: English | 1170 | Not measured | Only GPT-5 Nano measured |
| LMArena Vision: Chinese | 1176 | Not measured | Only GPT-5 Nano measured |
| LMArena Vision: reading text | 1152 | Not measured | Only GPT-5 Nano measured |
| LMArena Vision: humor | 1110 | Not measured | Only GPT-5 Nano measured |
| Neither model has a result on the other 15 boards here | |||
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
| Benchmark | GPT-5 Nano | Grok 4.20 | 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
GPT-5 Nano costs less
Repository review
50K input + 3K output tokens
GPT-5 Nano costs less
Agent loop
200K input + 10K output tokens
GPT-5 Nano 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 | OpenAI GPT-5 Nano | SpaceXAI Grok 4.20 |
|---|---|---|
| Maker | OpenAI | xAI |
| Weights | No public weights listed | No public weights listed |
| Released | August 7, 2025 | March 31, 2026 |
| Context window | 400K | 2M |
| Input $/Mtok | $0.05 | $1.25 |
| Output $/Mtok | $0.40 | $2.50 |
| Coding index | Not benchmarked | 33.3 |
| Independent measurements behind it | 0 | 2 |
| Cost per solved task | $0.109 | $0.72 |
| Source | OpenRouter listing | OpenRouter listing |
Questions
Is GPT-5 Nano better than Grok 4.20 for coding?
Only Grok 4.20 has a coding score, 33.3 on the Vibe Coding Index; GPT-5 Nano has none, so the two cannot be ranked on coding. Pick GPT-5 Nano for output tokens 6.3x cheaper ($0.40 vs $2.50 per million) and a lower cost per solved task ($0.109 against $0.72).
Which is cheaper, GPT-5 Nano or Grok 4.20?
GPT-5 Nano costs $0.05 per million input tokens and $0.40 per million output tokens; Grok 4.20 costs $1.25 and $2.50. Per solved SWE-bench Verified task, GPT-5 Nano costs $0.109 and Grok 4.20 $0.72.
Which has the bigger context window, GPT-5 Nano or Grok 4.20?
Grok 4.20, with 2M tokens against 400K.
How many benchmarks is the GPT-5 Nano vs Grok 4.20 comparison based on?
34 benchmarks have a result for both models as of October 22, 2026. GPT-5 Nano's coding index rests on 0 independent benchmarks and Grok 4.20's on 2. Where only one model has a result, the page says so instead of naming a winner.