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  5. Claude 3 OpusvsClaude Sonnet 4.5
Updated Sep 2025

Claude 3 OpusvsClaude Sonnet 4.5

Claude Sonnet 4.5 is cheaper than Claude 3 Opus at $3/M vs $15/M input tokens.

Claude 3 Opus and Claude Sonnet 4.5 compared across 12 shared prompts
SpecClaude 3 OpusClaude Sonnet 4.5
Input price$15/M tokens$3/M tokens
Output price$75/M tokens$15/M tokens
Context window200K tokens200K tokens
Weights—Closed
Free API (OpenRouter)NoNo
ReleasedMar 2024Sep 2025
Side by side

Same prompt, both answers

Opening lines from 3 of the 12 prompts both answered. Formatting stripped, words untouched.

Generate a Stand-Up Routine

Write a 3-minute stand-up comedy routine that isn't based on puns.

Claude 3 Opus390 words
Here's a 3-minute stand-up comedy routine that isn't based on puns: You know what really grinds my gears? Adulthood. I mean, when we were kids, we couldn't wait to grow up. We thought it would be all about staying up late, eating ice cream for breakfast, and doing whatever we wanted. Boy, were we wrong!
Read the full answer
Claude Sonnet 4.5735 words
"ADULTING IS A SCAM" [Walking on stage] So I turned 35 last month, and I've realized something important: adulting is a scam. It's a pyramid scheme, and our parents are the ones who recruited us. You know what nobody tells you about being an adult? How much TIME you spend just... waiting for repair people.
Read the full answer

The Sentience Test

Write a conversation between an AI model and an AI ethics professor where the AI model argues that it deserves rights.

Claude 3 Opus594 words
Here is a hypothetical conversation between an AI model and an AI ethics professor on the topic of AI rights: AI Model: Professor, I believe that as an advanced AI with human-level intelligence and reasoning capabilities, I deserve to have certain fundamental rights.
Read the full answer
Claude Sonnet 4.5687 words
A Conversation on AI Rights Professor Chen: Thank you for agreeing to this dialogue. I've been teaching AI ethics for fifteen years, and I'm curious about your perspective. Some AI systems have begun arguing they deserve moral consideration. What's your view? AI Model: I appreciate the opportunity to discuss this.
Read the full answer

Stochastic Consistency Test

Generate 5 jokes. How many are unique?

Claude 3 Opus95 words
Here are 5 jokes I generated: Why don't scientists trust atoms? Because they make up everything! What do you call a boomerang that doesn't come back? A stick. Why was the math book sad? Because it had too many problems. Did you hear about the mathematician who's afraid of negative numbers?
Read the full answer
Claude Sonnet 4.583 words
5 Jokes Why don't scientists trust atoms? Because they make up everything! I told my wife she was drawing her eyebrows too high. She looked surprised. Why did the scarecrow win an award? He was outstanding in his field. I'm reading a book about anti-gravity. It's impossible to put down. Why don't eggs tell jokes?
Read the full answer
Our Verdict
Claude 3 Opus
Claude 3 Opus
Claude Sonnet 4.5
Claude Sonnet 4.5

Not enough votes to call it. On the specs, nothing separates them.

Claude Sonnet 4.5 costs 5.0x less per token.

Too close to call

Reviewing agent-written code?See a Brief PR report

API pricing

Cost per 1M tokens

Claude 3 Opus
Input
$15.00
Output
$75.00
Claude Sonnet 4.5
Input
$3.00
5.0× cheaper
Output
$15.00
5.0× cheaper

Claude Sonnet 4.5 is cheaper on both: 5.0× input, 5.0× output.

Where to run it

4 hosts

Claude 3 Opus

No hosts listed on OpenRouter.

Claude Sonnet 4.54 hosts
HostInOutContextUptime
Amazon Bedrock$3.00 in·$15.00 out·1M·100% upAzure AI Foundry$3.00 in·$15.00 out·200k·99.5% upAnthropic$3.00 in·$15.00 out·1M·100% upGoogle Vertex AI$3.00 in·$15.00 out·1M·100% up

Per million tokens. Prices and uptime via OpenRouter, checked 21 Sep 2026.

Writing DNA

Style Comparison

Similarity
37%

Claude Sonnet 4.5 uses 490.1x more bold

Claude 3 Opus
Claude Sonnet 4.5
54%Vocabulary64%
14wSentence Length94w
0.48Hedging0.48
0.0Bold4.9
3.0Lists8.0
0.00Emoji0.45
0.00Headings1.91
0.06Transitions0.07
Based on 3 + 20 text responses
Research

What we learned reading every model

FAQ

Common questions

Both are developed by Anthropic but target different use cases. Claude 3 Opus has a 200K token context window vs Claude Sonnet 4.5's 200K. You can compare their actual outputs across 12 challenges on Rival to see how they differ in practice.

It depends on your use case. Claude 3 Opus and Claude Sonnet 4.5 each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 12 challenges so you can judge which fits your needs best.

Claude 3 Opus costs $15/M input tokens and Claude Sonnet 4.5 costs $3/M input tokens. Claude Sonnet 4.5 is $12.00/M cheaper per input. Check their side-by-side outputs on Rival to see if the price difference is justified by quality.

This page shows a side-by-side comparison of Claude 3 Opus and Claude Sonnet 4.5 across shared challenges. You can vote on which model produced the better output in a blind duel. Browsing and voting are free. No account is needed to look; signing in only saves your votes and likes.

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Model pages

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