The two are evenly matched.Claude Sonnet 4.5 is better at facts; o3-pro at following instructions.
Scores updated · 9 tests both models report · How we compare
Where each one wins
Tests won in each of the three 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.
Facts 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.
Claude Sonnet 4.5 costs 82% 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 Sonnet 4.5 pulls ahead
- Abstract visual puzzles that people can solveARC-AGI-2+8.7points ahead
Where o3-pro pulls ahead
- Keeps track of context across a multi-turn chatMulti-Challenge+7.1points ahead
- Graduate-level biology, physics and chemistry questionsGPQA Diamond+1.1points ahead
Every test, side by side
All 9 tests both models report. The winning score is in its model's colour; marks a score checked independently.
ReasoningEven
- ARC-AGI-2Claude Sonnet 4.5 by 8.713.64.9+8.7
- GPQA Diamondo3-pro by 1.183.484.5+1.1
FactsClaude Sonnet 4.5
- Vectara HHEM hallucination ratelower is betterClaude Sonnet 4.5 by 11.31223.3+11.3
Following instructionso3-pro
- Multi-Challengeo3-pro by 7.155.362.4+7.1
Other results5 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.
- vectara_factual_consistencyClaude Sonnet 4.5 by 11.38876.7+11.3
- ARC-AGI-1Claude Sonnet 4.5 by 4.463.759.3+4.4
- vectara_answer_rateo3-pro by 4.495.6100+4.4
- AA Intelligenceo3-pro by 1.220.721.9+1.2
- vectara_avg_summary_lengthtie127.8127.4tie
Questions people ask
Which is better, Claude Sonnet 4.5 or o3-pro?
Claude Sonnet 4.5 and o3-pro each win one of the three areas where both have results. Claude Sonnet 4.5 wins facts; o3-pro wins following instructions. Claude Sonnet 4.5 costs 82% less. They are level on reasoning.
Which is cheaper?
Claude Sonnet 4.5 costs $3.00 per million input tokens and $15.00 per million output tokens; o3-pro costs $20.00 and $80.00. That makes Claude Sonnet 4.5 about 82% cheaper for the same work.
How do you compare the two?
We use the 9 benchmark tests both models have published scores on. The verdict counts the 4 tests in the eight capability areas, and a gap under one point (ten on rating-style scales) counts as a tie. The other 5 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.