Claude Models

When to Use Opus vs Sonnet vs Haiku

The mistake most people make is using Opus for everything. Three questions tell you the right model every time.

Most people pour Opus for every cup. But the right model depends on what you're actually doing — strategy, language, or mechanical work. This guide gives you a decision tree, 12 worked examples, and the actual cost numbers.

The Decision Tree

Three questions. Stop at the first "yes."

Question 1

Is this strategic?

"Will the answer shape a real decision — pricing, positioning, hiring, money, a public commitment?"

YES→ Use Opus. The stakes justify premium reasoning.

NO→ Continue to Q2.

Question 2

Does the wording matter?

"Will a human read this exact output? Client copy, published content, an important email?"

YES→ Use Sonnet. The everyday workhorse — strong at language, drafting, judgment.

NO→ Continue to Q3.

Question 3

Is speed or volume the priority?

"Do I want this to feel instant? Is the task mechanical — formatting, extracting, tagging?"

YES→ Use Haiku. Fast, cheap, accurate enough for routine work.

NO→ Default to Sonnet.

💡 The 80/20 rule: When in doubt, default to Sonnet. It's the right pick roughly 80% of the time. Upgrade to Opus only when you can name the strategic stake. Drop to Haiku when you notice yourself doing the same routine task more than twice.

12 Worked Examples

The right model for each, plus a one-line why

#	Task	Pick	Why
1	Drafting an Instagram caption	Sonnet	Voice and word choice matter; Haiku reads flat.
2	Outlining a 6-month content strategy	Opus	Multi-variable, strategic, hard to redo if wrong.
3	Reformatting a list into bullet points	Haiku	Mechanical. Opus here = waste of money.
4	Summarising 10 articles into one digest	Sonnet	Synthesis needs nuance, but not deep reasoning.
5	Competitive teardown of 3 brands' positioning	Opus	Strategic call you'll act on. Worth the cents.
6	Quick fact lookup ("when did X launch?")	Haiku	One-shot, factual, no judgment needed.
7	Reviewing a contract clause for risk	Opus	High-stakes, ambiguity-heavy, real consequences.
8	Tagging customer feedback by theme	Haiku	Repetitive classification — Haiku nails it at scale.
9	Architecting a new automation system	Opus	Design decisions compound; hard to undo later.
10	Writing a small utility function	Sonnet	Common code, but you want it correct first try.
11	Daily email inbox triage / summary	Haiku	Volume + speed beat depth.
12	Brainstorming product names	Sonnet	Creative range matters; Haiku is too literal.

What It Actually Costs

API prices per 1M tokens (2026)

Model	Input	Output	Daily 1hr use / mo
Haiku 4.5	$1	$5	~$3.15/mo
Sonnet 4.6	$3	$15	~$9.45/mo
Opus 4.7	$5	$25	~$15.75/mo

Sonnet ≈ a Netflix subscription for daily use. Most people massively overestimate the cost.

Opus is only ~1.7× Sonnet — not "10× expensive" like older versions used to be. Pricing repriced down in 2025.

Haiku is so cheap that pinching pennies on Haiku tasks isn't worth your time. Spend the savings on better prompts instead.

Note: API costs apply when building automations. Claude.ai Pro chat is a flat $20/mo and these numbers don't apply directly.

Tasks That Belong in Haiku

Move these off Opus immediately

Summarising emails or Slack threads

Reformatting lists, bullet points, JSON, CSVs

Tagging or categorising (sentiment, topic, priority)

Translating short snippets between languages

Generating subject lines, alt text, meta descriptions

Extracting structured data (names, dates, prices) from a paragraph

Spelling, grammar, capitalisation fixes

Quick definitions and fact lookups

Daily email inbox triage / summary

Drafting routine messages (booking confirmations, RSVPs, intros)

First-pass classification before a human reviewer

🎯 Rule of thumb: If the task has one right answer and you wouldn't pay a human more than $5 to do it, it's a Haiku task.