🚫 Idioms to Avoid in IELTS – What Sounds Too Informal?

While idioms can help you sound fluent in the IELTS Speaking test, using the wrong type of idiom — especially overly informal or clichéd ones — can hurt your score. This is especially true in the Writing test, where formality is essential. In this guide, we’ll list idioms to avoid, explain why, and offer safer alternatives.

❌ Why You Should Avoid Certain Idioms

⚠️ They sound too casual or slangy for academic settings
⚠️ They may be misunderstood by the examiner
⚠️ Many are clichés or regionally limited
⚠️ They distract from clarity and reduce lexical precision

🛑 Informal or Risky Idioms to Avoid

Overused/Informal Idiom	Why Avoid It	Better Alternative
Hit the nail on the head	Too clichéd	Accurately point out / Clearly express
Out of the blue	Sounds too casual	Unexpectedly / Suddenly
Break a leg	Too idiomatic and irrelevant	Wish someone success
Spill the beans	Very informal/slangy	Reveal the truth / Disclose information
Piece of cake	Too childish or overused	Very easy / Straightforward
Cost an arm and a leg	Overused, informal	Very expensive / Highly priced

📌 General Rule for IELTS Writing

DO NOT use idioms in Task 1 or Task 2 essays. Stick to formal, clear, and academic language. You may use fixed phrases like:

“It is widely believed that...”
“A growing number of people...”
“In contrast to popular belief...”

✅ Safe Idioms for Speaking

If you want to show natural fluency in Speaking, choose idioms that are:

✔️ Understandable globally
✔️ Contextually appropriate
✔️ Used naturally in informal conversation

Examples:

“Over the moon” – very happy
“Under the weather” – not feeling well
“A tough nut to crack” – difficult problem

🧠 Practice Activity

Replace the idioms below with a more formal version:

My final exam was a piece of cake.
He hit the nail on the head with his answer.
It cost me an arm and a leg to get into that course.

Sample Answers:

My final exam was very easy.
He answered the question very accurately.
The course was extremely expensive.

🎯 Final Advice

Using idioms can help in Speaking — but only when they’re used accurately and sound natural. For Writing, avoid them entirely. Keep your language formal, academic, and precise to maximize your IELTS score.

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