Last verified 2026-02-11 (left) · 2026-02-11 (right)

Claude Opus 4.5 (Legacy) vs Claude Sonnet 4.5 — Pricing & Capability Comparison

Claude Opus 4.5 (Legacy) charges $5.00 per million input tokens and $25.00 per million output tokens. Claude Sonnet 4.5 comes in at $3.00 / $15.00. Context windows span 200K vs 200K tokens respectively.

TL;DR — Quick Comparison

✓Claude Sonnet 4.5 is cheaper overall: $18.00 per 1M tokens (in+out) vs $30.00 for Claude Opus 4.5 (Legacy) — saves $12.00 per 1M tokens
✓Input pricing: Claude Opus 4.5 (Legacy) $5.00/1M vs Claude Sonnet 4.5 $3.00/1M
✓Output pricing: Claude Opus 4.5 (Legacy) $25.00/1M vs Claude Sonnet 4.5 $15.00/1M
✓Context window: Claude Opus 4.5 (Legacy) offers more (200K vs 200K)
✓Use our calculator below to estimate costs for your specific usage pattern

Input price (per 1M)

Claude Opus 4.5 (Legacy)

$5.00

Claude Sonnet 4.5

$3.00

Claude Sonnet 4.5 leads here

Output price (per 1M)

Claude Opus 4.5 (Legacy)

$25.00

Claude Sonnet 4.5

$15.00

Claude Sonnet 4.5 leads here

Context window

Claude Opus 4.5 (Legacy)

200,000 tokens

Claude Sonnet 4.5

200,000 tokens

Claude Opus 4.5 (Legacy) leads here

Cached input

Claude Opus 4.5 (Legacy)

$0.500

Claude Sonnet 4.5

$0.300

Claude Sonnet 4.5 leads here

Which one should you choose?

Skip the spreadsheet if you just need the practical takeaway. Use these rules when deciding between Claude Opus 4.5 (Legacy) and Claude Sonnet 4.5.

Choose Claude Sonnet 4.5 if input tokens dominate your bill

Claude Sonnet 4.5 has the lower input rate, which usually matters most for chat, RAG, classification, and long-prompt workflows where prompt volume stays much larger than generated output.

Choose Claude Sonnet 4.5 if you generate long answers

Claude Sonnet 4.5 is cheaper on output tokens, so it tends to win for report generation, coding assistance, reasoning traces, and any workflow where completions are long.

Choose Claude Opus 4.5 (Legacy) if context size is the blocker

Claude Opus 4.5 (Legacy) offers the larger published context window, which is more important than small pricing differences when you need to fit large files, long chats, or multi-document prompts into one request.

Cost comparison for 10K-token workloads

Side-by-side pricing for identical workloads (10,000 total tokens per request) across different distributions.

Scenario	Claude Opus 4.5 (Legacy)	Claude Sonnet 4.5	Claude Opus 4.5 (Legacy) cached	Claude Sonnet 4.5 cached
Balanced conversation 50% input · 50% output	$0.150	$0.0900	$0.128	$0.0765
Input-heavy workflow 80% input · 20% output	$0.0900	$0.0540	$0.0540	$0.0324
Generation heavy 30% input · 70% output	$0.190	$0.114	$0.177	$0.106
Cached system prompt 90% cached input · 10% fresh output	$0.0700	$0.0420	$0.0295	$0.0177

Frequently asked questions

Which is cheaper: Claude Opus 4.5 (Legacy) or Claude Sonnet 4.5?

Claude Sonnet 4.5 is cheaper for input tokens at $3.00 per 1M tokens compared to $5.00. For output, Claude Sonnet 4.5 costs $15.00 per 1M tokens versus $25.00 for Claude Opus 4.5 (Legacy).

What is the cost per 1M tokens for Claude Opus 4.5 (Legacy)?

Claude Opus 4.5 (Legacy) pricing: $5.00 per 1M input tokens and $25.00 per 1M output tokens. Context window: 200,000 tokens.

What is the cost per 1M tokens for Claude Sonnet 4.5?

Claude Sonnet 4.5 pricing: $3.00 per 1M input tokens and $15.00 per 1M output tokens. Context window: 200,000 tokens.

How much does it cost per 1K tokens?

Per 1K tokens: Claude Opus 4.5 (Legacy) costs $0.0050 input / $0.0250 output. Claude Sonnet 4.5 costs $0.0030 input / $0.0150 output. This is useful for calculating small-scale usage costs.

Which model supports a larger context window?

Claude Opus 4.5 (Legacy) offers 200,000 tokens (200K) versus 200K for Claude Sonnet 4.5.

What is the estimated monthly cost for typical usage?

For a typical workload of 10M input + 2M output tokens per month: Claude Opus 4.5 (Legacy) would cost approximately $100.00, while Claude Sonnet 4.5 would cost $60.00. Claude Sonnet 4.5 is more economical for this usage pattern.

Do these models support prompt caching?

Claude Opus 4.5 (Legacy) supports prompt caching at $0.500 per 1M cached tokens, reducing costs for repeated context by up to 90%. Claude Sonnet 4.5 supports caching at $0.300 per 1M tokens, saving up to 90%.

Which model is best for my use case?

Choose Claude Sonnet 4.5 for cost-sensitive applications with high input volume. Choose Claude Opus 4.5 (Legacy) if you need 200K context for long documents or conversations. Consider prompt caching if you have repeated context. Use our token calculator to model your specific usage pattern.