Claude Opus 4.5 vs Grok 4 Fast
Wins 6 of 7 areas
Coding · Reasoning · Facts · Images and charts · Long documents · Following instructions
Wins 0 of 7 areas
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Claude Opus 4.5 is the stronger all-rounder.Grok 4 Fast is cheaper.
Scores updated · 26 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.
- ReasoningHard problems that need careful thinking40Claude Opus 4.54 of 4 tests
- CodingWriting and fixing software30Claude Opus 4.53 of 3 tests
- FactsGetting facts right instead of making them up30Claude Opus 4.53 of 3 tests
- Images and chartsUnderstanding pictures, charts and video10Claude Opus 4.51 of 1 test
- Long documentsFinding answers in very long texts10Claude Opus 4.51 of 1 test
- Following instructionsDoing exactly what it is asked10Claude Opus 4.51 of 1 test
- AgentsCarrying out multi-step tasks on its own11Even1 each
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 98% less for the same work.
The biggest differences
The tests each model wins by the widest margin, up to three each. Scores are out of 100.
Where Claude Opus 4.5 pulls ahead
- Abstract visual puzzles that people can solveARC-AGI-2+32.3points ahead
- Hard command-line tasks in a real terminalTerminal-Bench Hard+28.1points ahead
- Answers hard knowledge questions correctlyAA-Omniscience · Accuracy+23.8points ahead
Where Grok 4 Fast pulls ahead
- Finds hard-to-locate facts by browsing the webBrowseComp+7.9points ahead
Every test, side by side
All 26 tests both models report. The winning score is in its model's colour; marks a score checked independently.
CodingClaude Opus 4.5
- LMArena · WebDevClaude Opus 4.5 by 310 rating points14691159+310 rating
- Terminal-Bench HardClaude Opus 4.5 by 28.14718.9+28.1
- SciCodeClaude Opus 4.5 by 5.349.544.2+5.3
AgentsEven
- GDPValClaude Opus 4.5 by 21.647.325.7+21.6
- BrowseCompGrok 4 Fast by 7.93744.9+7.9
ReasoningClaude Opus 4.5
- ARC-AGI-2Claude Opus 4.5 by 32.337.65.3+32.3
- Humanity's Last ExamClaude Opus 4.5 by 1130.119.1+11
- GPQA DiamondClaude Opus 4.5 by 1.986.684.7+1.9
- CritPtClaude Opus 4.5 by 1.74.62.9+1.7
FactsClaude Opus 4.5
- AA-Omniscience · AccuracyClaude Opus 4.5 by 23.846.622.8+23.8
- Vectara HHEM hallucination ratelower is betterClaude Opus 4.5 by 9.310.920.2+9.3
- AA-Omniscience · Non-hallucinationClaude Opus 4.5 by 7.33931.7+7.3
Images and chartsClaude Opus 4.5
- MMMU-ProClaude Opus 4.5 by 12.27461.8+12.2
Following instructionsClaude Opus 4.5
- IFBenchClaude Opus 4.5 by 7.55850.5+7.5
Other results11 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 Opus 4.5 by 43.914-29.9+43.9
- ARC-AGI-1Claude Opus 4.5 by 33.58248.5+33.5
- τ²-Bench Telecom (AA run)Claude Opus 4.5 by 23.789.565.8+23.7
- Artificial Analysis Coding IndexClaude Opus 4.5 by 20.447.827.4+20.4
- AA Agentic IndexClaude Opus 4.5 by 20.159.639.5+20.1
- AA IntelligenceClaude Opus 4.5 by 11.229.117.9+11.2
- vectara_factual_consistencyClaude Opus 4.5 by 9.389.179.8+9.3
- LiveCodeBenchClaude Opus 4.5 by 78780+7
- vectara_avg_summary_lengthGrok 4 Fast by 59.4 rating points114.5173.9+59.4 rating
- AIME 2025tie92.892tie
- vectara_answer_ratetie98.799.5tie
Questions people ask
Which is better, Claude Opus 4.5 or Grok 4 Fast?
Claude Opus 4.5 wins six of the seven areas where both have results: coding, reasoning, facts, images and charts, long documents and following instructions. Grok 4 Fast wins none, but costs 98% less. They are level on agents.
Which is better for coding?
Claude Opus 4.5. It wins 3 of the 3 coding tests both models report; Grok 4 Fast wins none.
Which is cheaper?
Claude Opus 4.5 costs $5.00 per million input tokens and $25.00 per million output tokens; Grok 4 Fast costs $0.20 and $0.50. That makes Grok 4 Fast about 98% cheaper for the same work.
How do you compare the two?
We use the 26 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 11 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.