Claude Sonnet 4.5 vs Grok 4 Fast
Wins 4 of 7 areas
Coding · Facts · Images and charts · Following instructions
Wins 3 of 7 areas
Agents · Reasoning · Long documents
Claude Sonnet 4.5 wins more areas, narrowly.Grok 4 Fast is cheaper and better at reasoning.
Scores updated · 28 tests both models report · How we compare
Where each one wins
Tests won in each of the seven areas where both have results. Each piece is one test, so a longer bar means more evidence; grey means the two scored within a point of each other.
- CodingWriting and fixing software30Claude Sonnet 4.53 of 3 tests
- FactsGetting facts right instead of making them up30Claude Sonnet 4.53 of 3 tests
- Images and chartsUnderstanding pictures, charts and video10Claude Sonnet 4.51 of 1 test
- Following instructionsDoing exactly what it is asked10Claude Sonnet 4.51 of 1 test
- ReasoningHard problems that need careful thinking13Grok 4 Fast3 of 4 tests
- AgentsCarrying out multi-step tasks on its own02Grok 4 Fast2 of 2 tests
- Long documentsFinding answers in very long texts01Grok 4 Fast1 of 1 test
Images and charts, long documents and following instructions rest on a single test each.
What it costs
Prices per million tokens, roughly 750,000 words. The bars show the cost of a million tokens read plus a million written.
Grok 4 Fast costs 96% less for the same work.
The biggest differences
The three tests each model wins by the widest margin. Scores are out of 100.
Where Claude Sonnet 4.5 pulls ahead
- Avoids making up answers it doesn't knowAA-Omniscience · Non-hallucination+19.2points ahead
- Hard command-line tasks in a real terminalTerminal-Bench Hard+16.7points ahead
- Answers hard knowledge questions correctlyAA-Omniscience · Accuracy+10.1points ahead
Where Grok 4 Fast pulls ahead
- Finds hard-to-locate facts by browsing the webBrowseComp+20.8points ahead
- Real work tasks from 44 professionsGDPVal+5.2points ahead
- Research-level physics problemsCritPt+1.8points ahead
Every test, side by side
All 28 tests both models report. The winning score is in its model's colour; marks a score checked independently.
CodingClaude Sonnet 4.5
- LMArena · WebDevClaude Sonnet 4.5 by 234 rating points13931159+234 rating
- Terminal-Bench HardClaude Sonnet 4.5 by 16.735.618.9+16.7
- SciCodeClaude Sonnet 4.5 by 1.545.744.2+1.5
AgentsGrok 4 Fast
- BrowseCompGrok 4 Fast by 20.824.144.9+20.8
- GDPValGrok 4 Fast by 5.220.525.7+5.2
ReasoningGrok 4 Fast
- ARC-AGI-2Claude Sonnet 4.5 by 8.313.65.3+8.3
- CritPtGrok 4 Fast by 1.81.12.9+1.8
- GPQA DiamondGrok 4 Fast by 1.383.484.7+1.3
- Humanity's Last ExamGrok 4 Fast by 1.317.819.1+1.3
FactsClaude Sonnet 4.5
- AA-Omniscience · Non-hallucinationClaude Sonnet 4.5 by 19.250.931.7+19.2
- AA-Omniscience · AccuracyClaude Sonnet 4.5 by 10.132.922.8+10.1
- Vectara HHEM hallucination ratelower is betterClaude Sonnet 4.5 by 8.21220.2+8.2
Images and chartsClaude Sonnet 4.5
- MMMU-ProClaude Sonnet 4.5 by 6.968.761.8+6.9
Following instructionsClaude Sonnet 4.5
- IFBenchClaude Sonnet 4.5 by 6.857.350.5+6.8
Other results13 tests, not counted
Tests outside the eight areas. They are not counted above: several are summary scores built from other tests, or the same test under another name.
- AA-OmniscienceClaude Sonnet 4.5 by 29.8-0.1-29.9+29.8
- Artificial Analysis Coding IndexClaude Sonnet 4.5 by 24.752.127.4+24.7
- AA Agentic IndexGrok 4 Fast by 2217.539.5+22
- HMMT 2025Grok 4 Fast by 18.774.693.3+18.7
- ARC-AGI-1Claude Sonnet 4.5 by 15.263.748.5+15.2
- τ²-Bench Telecom (AA run)Claude Sonnet 4.5 by 12.378.165.8+12.3
- LiveCodeBenchGrok 4 Fast by 97180+9
- vectara_factual_consistencyClaude Sonnet 4.5 by 8.28879.8+8.2
- AIME 2025Grok 4 Fast by 58792+5
- vectara_avg_summary_lengthGrok 4 Fast by 46.1 rating points127.8173.9+46.1 rating
- vectara_answer_rateGrok 4 Fast by 3.995.699.5+3.9
- AA IntelligenceClaude Sonnet 4.5 by 2.820.717.9+2.8
- BrowseComp-ZHGrok 4 Fast by 2.642.445+2.6
Questions people ask
Which is better, Claude Sonnet 4.5 or Grok 4 Fast?
Claude Sonnet 4.5 wins four of the seven areas where both have results: coding, facts, images and charts and following instructions. Grok 4 Fast wins agents, reasoning and long documents, and costs 96% less.
Which is better for coding?
Claude Sonnet 4.5. It wins 3 of the 3 coding tests both models report; Grok 4 Fast wins none.
Which is cheaper?
Claude Sonnet 4.5 costs $3.00 per million input tokens and $15.00 per million output tokens; Grok 4 Fast costs $0.20 and $0.50. That makes Grok 4 Fast about 96% cheaper for the same work.
How do you compare the two?
We use the 28 benchmark tests both models have published scores on. The verdict counts the 15 tests in the eight capability areas, and a gap under one point (ten on rating-style scales) counts as a tie. The other 13 are listed but not counted, because several are summary scores or repeat a test. Each score is the one shown on the model's own page.