Claude · Models
Claude Sonnet vs Opus: When to Use Each Model
A practical guide to choosing between Claude Sonnet 4.6, Claude Opus 4.8, and Claude Haiku 4.5 — by cost, speed, capability, and context window.
Model specs verified June 9, 2026 · source
The short answer
Use Claude Sonnet 4.6 as your default — it handles roughly 80% of prompting and coding work at near-flagship quality, faster, and at a fraction of the cost. Escalate to Claude Opus 4.8 only on the specific tasks where Sonnet actually fails: large refactors, dense analysis, hard debugging, long agentic runs. Drop to Claude Haiku 4.5 for high-volume, low-judgement jobs. The model is rarely the bottleneck — a weak prompt usually is.
Sonnet vs Opus vs Haiku at a glance
| Model | Tier | Input / Output ($/M tok) | Context | Speed | Best for |
|---|---|---|---|---|---|
| Claude Opus 4.8 | flagship | $5 / $25 | 1M | moderate | Most capable Opus-tier model for complex reasoning and agentic coding |
| Claude Sonnet 4.6 | workhorse | $3 / $15 | 1M | fast | Best combination of speed and intelligence |
| Claude Haiku 4.5 | fast | $1 / $5 | 200K | fastest | Fastest model with near-frontier intelligence |
Specs and prices verified against Anthropic's model docs on 2026-06-09. Claude Sonnet 4.6 highlighted as the recommended default.
When should you use Sonnet vs Opus?
Match the task to the model. When in doubt, start on Claude Sonnet 4.6 and only escalate the prompts that actually stall.
| Task | Pick | Why |
|---|---|---|
| Blog posts, marketing copy, email drafts | Claude Sonnet 4.6 | Quality is indistinguishable at this complexity; Sonnet is faster. |
| Summarising or extracting from long documents | Claude Sonnet 4.6 | Full context window, low cost per run. |
| Everyday coding, small-to-medium features | Claude Sonnet 4.6 | Handles most code correctly first try. |
| Large multi-file refactors, architecture decisions | Claude Opus 4.8 | Reasoning depth prevents compounding errors. |
| Hard debugging where Sonnet keeps missing | Claude Opus 4.8 | Escalate only on the prompts that actually stall. |
| Dense analysis: legal, financial, research synthesis | Claude Opus 4.8 | Nuance and multi-step logic justify the premium. |
| Long agentic runs with many tool calls | Claude Opus 4.8 | One wrong turn early compounds across the run. |
| Classification, tagging, routing at scale | Claude Haiku 4.5 | Cheapest and fastest; judgement is light. |
| High-volume batch jobs (thousands of prompts) | Claude Haiku 4.5 | Cost difference vs Opus is dramatic at volume. |
The cost difference, in plain numbers
Claude Sonnet 4.6 costs $3/M input and $15/M output. Claude Opus 4.8 costs $5/M input and $25/M output. On output tokens — the expensive part of most generation work — Opus is 1.7x the price of Sonnet.
That gap is invisible on a single prompt and brutal at scale. Run a hundred coding sessions a month on Opus when Sonnet would have produced the same result, and you have paid a multiple for no extra quality. The discipline is not "always use the cheapest" — it is "use the cheapest model that gets the task right."
Claude Haiku 4.5 sits below both at $1/M input and $5/M output. For batch classification or tagging across thousands of items, that is where the real savings live.
The mistake most people make
Reaching for Opus when the prompt is the problem
The most common failure mode: a prompt returns a weak answer on Claude Sonnet 4.6, so the user upgrades to Claude Opus 4.8 and pays the premium — when the real fix was a clearer prompt. Vague instructions, missing context, and no examples will hobble any model. Opus papers over a bad prompt at 1.7x the output cost.
Before you upgrade the model, upgrade the prompt:
Run that on Claude Sonnet 4.6 first. If a fully-specified prompt still fails, you have a genuine reasoning task — and that is exactly when Claude Opus 4.8 earns its price. The free Prompt Grader scores your version of this structure and shows you exactly which part is missing.
Frequently asked questions
What is the difference between Claude Sonnet 4.6 and Claude Opus 4.8?+
Claude Opus 4.8 is Anthropic's flagship model — built for the hardest reasoning and agentic coding work — at $5/$25 per million input/output tokens. Claude Sonnet 4.6 is the workhorse: nearly as smart for everyday tasks, faster, and cheaper at $3/$15 per million tokens. For 80% of prompting and coding work, Sonnet is the right default. Reach for Opus only when a task genuinely stalls a smaller model.
When should I use Opus instead of Sonnet?+
Use Opus when the task needs multi-step reasoning that Sonnet gets wrong — large refactors across many files, dense legal or financial analysis, tricky debugging, or long agentic runs where a single wrong turn compounds. If Sonnet produces a correct answer on the first or second try, Opus is wasted money. A good rule: draft on Sonnet, escalate to Opus only on the specific prompts where Sonnet fails.
Is Claude Sonnet 4.6 good enough for most prompting?+
Yes. Claude Sonnet 4.6 handles content writing, summarisation, data extraction, most coding, and structured-output prompts at near-flagship quality — faster and at 40% lower input cost than Claude Opus 4.8. Most people who think they need Opus are actually fighting a weak prompt, not a weak model. Tighten the prompt before you upgrade the model.
Where does Claude Haiku 4.5 fit in?+
Claude Haiku 4.5 is the fast, cheap tier at $1/$5 per million tokens — the fastest of the three. Use it for high-volume, low-judgement work: classification, tagging, simple extraction, routing, first-pass drafts you will edit. It is not the model for nuanced reasoning, but for batch jobs where you run thousands of prompts, the cost difference versus Opus is dramatic.
Do Sonnet and Opus have the same context window?+
Claude Opus 4.8 and Claude Sonnet 4.6 both offer a 1M-token context window, so window size is not the deciding factor between them. Claude Haiku 4.5 is smaller at 200K tokens. If you are feeding an entire codebase or a long document, either Sonnet or Opus will hold it — pick on reasoning need and cost, not context.
How much cheaper is Sonnet than Opus in practice?+
Claude Sonnet 4.6 input tokens cost $3/M versus $5/M for Claude Opus 4.8, and output is $15/M versus $25/M. On a typical coding session that reads a lot of context and writes moderate output, Sonnet runs roughly 1.7x cheaper on output alone. Over a month of daily use that is the difference between a small bill and a large one.
Stop guessing which model to use
The model selector takes your task type and runs the choice for you. Once you know the model, the next lever is the prompt — that is where most of the quality lives. The free Prompt Grader scores yours and rewrites it.