Sonnet 5.5 vs Opus 5.5: Pricing, Speed and Which to Pick

Last updated: November 6, 2026. By Veer. Prices and specs checked on November 6, 2026 against Anthropic’s models overview, Claude Platform pricing, the Sonnet and Opus product pages, and claude.com/pricing. Independent scores from Artificial Analysis. This is a researched comparison built from public docs and third-party benchmarks, not a hands-on test.

Claude Sonnet 5.5 and Claude Opus 5.5 are Anthropic’s two workhorse models in the 5.5 family. Opus shipped on September 22, 2026; Sonnet followed on September 28. They share the same context window and knowledge cutoff, so the real decision is price, speed, and how hard the task is — not “which one can read a long file.”

Sonnet 5.5 vs Opus 5.5: the quick answer

Use Sonnet 5.5 for most coding, writing and agent loops. Use Opus 5.5 when the job needs longer autonomy, sharper judgment, or the best score you can buy inside Anthropic’s lineup. Anthropic’s own models overview calls Sonnet “the best combination of speed and intelligence” and Opus the model “for long-running agentic coding and knowledge work.” It also tells developers to “start with Claude Opus 5.5 for most workloads” if they’re unsure — which is the quality-first read, not the cost-first one.

Sources: models overview, pricing, Sonnet product page, Opus product page. All API prices are USD.

How much does Sonnet 5.5 vs Opus 5.5 cost on the API?

Opus 5.5 costs twice Sonnet 5.5 on every standard token rate. Input, output, cache reads and cache writes are all 2x. That means a chat reply, an agent step and a long-context job all roughly double when you switch models, unless Opus finishes the job with far fewer tokens.

Worked examples at list prices (no cache, no batch discount):

Prompt caching and the Message Batches API change the bill. Both models get a 50% Batch discount on input and output, per Anthropic’s pricing page. Cache hits are priced at 0.05x the base input rate on both 5.5 models ($0.10 for Sonnet, $0.20 for Opus). US-only inference (inference_geo: "us") adds a 1.1x multiplier on Claude 4.6 and later, including Sonnet 5.5 and Opus 5.5.

Opus also has a separate Fast mode at $8 input / $40 output per million tokens — double Opus’s already-premium rate — which Anthropic says can run up to 2.5x faster in Claude Code and on the Claude Platform. Sonnet has no matching Fast mode on the pricing table; it is already the faster of the two at standard rates.

Which is better for coding: Sonnet 5.5 or Opus 5.5?

Opus 5.5 leads on independent quality indexes; Sonnet 5.5 is usually the better coding default once you weigh speed and cost. Anthropic positions Sonnet for “well-scoped everyday tasks like fixing bugs and quickly iterating on features,” and Opus for “long-running work in large codebases” and multi-tool agents (Sonnet, Opus product pages).

On vendor-reported coding scores:

• Anthropic says Sonnet 5.5 scores 70.6% on Terminal-Bench 4.0, up from 10.3% for Sonnet 5, and that it sits about two points below Opus 5.5 on GDPval-AA (Sonnet 5.5 announcement).
• Anthropic reports Opus 5.5 at 66.4% on Terminal-Bench 4.0 (xhigh effort), 54.6% on FrontierCode v1.1 at default medium effort, and 52.5% on CursorBench 4.0 at default medium (Opus 5.5 announcement).

Those are Anthropic’s own charts, often at different effort settings, so they are not a clean head-to-head. For a same-suite read, Artificial Analysis (checked November 6, 2026) scores Opus 5.5 (max) at 59 on its Intelligence Index versus 55 for Sonnet 5.5 (max). At that max setting the cost per index task is almost identical — about $10.04 for Opus and $10.02 for Sonnet — because Opus used fewer output tokens (218M vs 335M across the index). Output speed favors Sonnet (151 tok/s vs 106 tok/s on those pages).

Practical takeaway: escalate to Opus for ambiguous multi-file refactors, multi-hour agents and cases where a wrong answer is expensive. Keep Sonnet as the default in Claude Code and API loops where you iterate often. For Claude Code vs OpenAI Codex limits and pricing, see our Claude Code vs Codex comparison.

Speed, effort and context window

Both models have a 1M-token context window and 128K max output; Sonnet is the faster of the two at standard pricing. Anthropic labels Sonnet’s comparative latency as Fast and Opus as Moderate on the models overview. The Sonnet product page also says Sonnet 5.5 generates outputs 30%+ faster than Sonnet 5.

Effort settings matter as much as the model name. Opus defaults to medium effort; Sonnet defaults to high on the API. Higher effort usually means more thinking tokens and a higher bill. Anthropic’s Sonnet announcement notes that in Claude Code and the apps, default effort is set to Medium, while the API exposes the control directly — so the same model can feel cheaper or more thorough depending on where you call it.

Neither model has a long-context surcharge inside the 1M window. That is a quiet advantage over some competitors that raise rates above a token threshold; we covered that angle in Sonnet 5.5 vs GPT-6.1 Sol.

Claude.ai access: free plan, Pro, Max and Ultra

Sonnet 5.5 is available on the free Claude.ai plan; Opus 5.5 needs Pro or higher. Anthropic’s Sonnet page says anyone can chat with Sonnet 5.5 on web, iOS and Android. The Opus page limits Opus 5.5 to Pro, Max, Ultra, Team and Enterprise. The claude.com/pricing feature table matches that: Sonnet is Yes across Free/Pro/Max/Ultra; Opus is No on Free and Yes on paid tiers. Claude Code is listed from Pro upward.

Current individual prices on Anthropic’s web pricing page (USD, tax extra):

UK readers paying through Apple’s App Store typically see Claude Pro at £20, Max at £119.99 and Ultra at £249.99 a month (VAT included), based on the UK listing checked for earlier TrustLoud posts. Anthropic’s web checkout shows local currency at pay time; the public pricing page is USD-only.

If you’re choosing a Claude plan rather than an API model, our Claude Max 5x vs 20x and best AI subscription for personal use guides cover the plan math. For a three-way $20-plan shootout, see ChatGPT Plus vs Claude Pro vs Google AI Pro.

Verdict: which should you pick?

Default to Sonnet 5.5. Switch to Opus 5.5 when the task is hard enough that a better answer is worth 2x the token bill. That is the cost-aware reading of Anthropic’s own product copy, and it matches how most API teams already run model routers.

• Choose Claude Sonnet 5.5 if you want the everyday coding and writing model, free Claude.ai access, faster responses, or high-volume agent steps where price compounds.
• Choose Claude Opus 5.5 if you run long autonomous coding agents, need the higher Artificial Analysis score, or hit quality ceilings on Sonnet at medium/high effort.
• Try Opus Fast mode only when latency matters more than cost — it is priced at $8 / $40 per million tokens.
• Keep Haiku 5.5 (from $0.10 / $0.50) for classification and routing; it is not a substitute for either model on hard agent work.

Prices move. Recheck platform.claude.com pricing before you lock in a production budget.

FAQ

Is Opus 5.5 twice as expensive as Sonnet 5.5?

Yes, on standard API list prices. Claude Opus 5.5 is $4 input and $20 output per million tokens; Claude Sonnet 5.5 is $2 and $10. Cache reads are $0.20 versus $0.10. Real bills can narrow if Opus finishes with fewer tokens, which Artificial Analysis observed at max effort on its Intelligence Index.

Can I use Opus 5.5 on the free Claude plan?

No. Anthropic makes Opus 5.5 available on Claude Pro, Max, Ultra, Team and Enterprise. Sonnet 5.5 is available on the free Claude.ai plan with lower usage limits.

Do Sonnet 5.5 and Opus 5.5 have the same context window?

Yes. Both have a 1 million token context window and up to 128K output tokens on the standard API. Both list a June 2026 reliable knowledge cutoff on Anthropic’s models overview.

Is Sonnet 5.5 better than Opus 5.5 for coding?

It depends on the job. Sonnet is usually the better default for everyday coding because it is faster and half the price. Opus leads on Artificial Analysis’ Intelligence Index (59 vs 55 at max, checked November 6, 2026) and is Anthropic’s pick for long-running agentic coding. Test both on your own repo before standardizing.

Does Opus 5.5 Fast mode cost more?

Yes. Fast mode for Claude Opus 5.5 is priced at $8 per million input tokens and $40 per million output tokens on the Claude Platform pricing page — double Opus’s standard rate — for up to about 2.5x faster speed, per Anthropic’s Opus product page.

Should I start with Sonnet or Opus in a new app?

For cost-sensitive production traffic, start with Sonnet 5.5 and route hard tasks to Opus 5.5. Anthropic’s docs suggest starting with Opus when you are unsure and optimizing later; that advice prioritizes quality over spend.

Sources

1. Anthropic models overview — specs, latency labels, effort defaults, retirement commitments.
2. Claude Platform pricing — token rates, cache, Batch, Fast mode, US-only 1.1x.
3. Claude Sonnet 5.5 model page and product page.
4. Claude Opus 5.5 model page and product page.
5. Introducing Claude Sonnet 5.5 (September 28, 2026).
6. Introducing Claude Opus 5.5 (September 22, 2026).
7. claude.com/pricing — Free / Pro / Max / Ultra feature matrix.
8. Artificial Analysis — Claude Sonnet 5.5 and Claude Opus 5.5 (checked November 6, 2026).