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"Idiomatic Language in IELTS Speaking: Use It Like a Band 8"

IELTS Speaking29 August 2026 · 7 min read · WiderAI Team

Idioms can raise your IELTS Speaking score, but only under one condition: they must sound like your language, not a decoration you attached for the examiner. Idiomatic language is mentioned in the higher bands of the Lexical Resource criterion, and this single fact has spawned an industry of "20 idioms for band 8" lists. The result is candidates announcing "it's raining cats and dogs" and "every cloud has a silver lining" in answers where no fluent speaker would ever say them — and losing credibility rather than gaining marks.

Here is what the criterion actually rewards. "Idiomatic language" in the examiner's sense is much broader than colourful proverbs. It includes phrasal verbs (put up with, run into, sort out), natural collocations (heavy traffic, bitterly cold, a close friend), conversational chunks (to be fair, it's a bit of a stretch, I can't be bothered), and everyday expressions (a big deal, out of my comfort zone, hit or miss). A candidate whose speech is full of these — used accurately, without effort — sounds idiomatic to an examiner even if they never produce a single textbook idiom.

So the strategy is not to memorise ten flashy idioms and deploy them. It is to shift your vocabulary learning towards natural chunks, master a small set deeply, and let precision beat decoration. Here is how.

What counts as idiomatic language in IELTS Speaking?

Examiners use "idiomatic" to describe language whose meaning or combination is conventional rather than literal — the way words actually go together in real English. Ranked by usefulness to you:

1. Phrasal verbs. The workhorses of spoken English: grow up, give up, look after, end up, figure out, get along with. Native speech is saturated with them, and they fit any topic. If you upgrade only one area, upgrade this one.
2. Collocations. Word partnerships that mark natural usage: you make a decision, take responsibility, do damage; traffic is heavy, competition is fierce, a schedule is packed. Wrong collocations (strong rain, do a mistake) are what make otherwise correct English sound foreign.
3. Conversational expressions. The chunks fluent speakers reach for constantly: to be honest, at the end of the day, it's not my thing, easier said than done, a win-win, the best of both worlds. These are idiomatic, low-risk, and never sound recited because they genuinely belong in conversation.
4. Classic idioms. Over the moon, once in a blue moon, break the ice. These are the smallest and riskiest category. Used perfectly, they add colour; used slightly wrongly, they are the most visible error in your whole test.

The proportions matter. In real fluent speech, categories one to three appear in nearly every sentence, while classic idioms might appear once in several minutes. Candidates who invert that ratio sound like they are performing English rather than speaking it.

Why do memorised idioms backfire?

Three failure modes, all of them familiar to every examiner.

The register clash. Many list-idioms are old-fashioned or literary. A twenty-year-old saying "it cost an arm and a leg, but I was over the moon" twice in one answer sounds like a phrasebook, because current speakers use these sparingly if at all. The examiner cannot credit as "natural idiomatic language" something that is conspicuously unnatural.

The forced fit. Memorised idioms get inserted where they almost work: "My hometown is the apple of my eye." (People, not towns, are the apple of someone's eye.) A near-miss idiom is worse than no idiom — under Lexical Resource, inaccurate use of less common vocabulary is precisely what holds candidates at the band below.

The delivery seam. An idiom you have rehearsed arrives with a tiny change of pace and tone — often preceded by a micro-pause and delivered with a flourish. Combined with simpler language everywhere else, it tells the examiner this phrase was installed for the test. One planted idiom can retroactively cheapen everything idiomatic you said before it.

The underlying principle: examiners reward language that reveals ability, and discount language that reveals preparation. An idiom only demonstrates ability when it appears effortlessly, in the right place, at the right register — which is exactly what memorising a list cannot produce.

Which idiomatic expressions are actually worth learning?

Learn a compact set with maximum coverage — expressions that fit dozens of topics and current, neutral registers. A starter set that earns its place:

• For likes and habits: I'm really into..., it's not my cup of tea (still current), I do it religiously, whenever I get the chance
• For difficulty and effort: easier said than done, a steep learning curve, out of my depth, I had to push myself
• For frequency and change: once in a while, now and then, it's taken off recently, it died down
• For evaluation: hit or miss, a mixed blessing, the best of both worlds, not worth the hassle, a no-brainer
• For feelings: I was thrilled, gutted, it caught me off guard, a huge relief, nerve-racking

Two rules govern how you learn them. First, learn each expression inside a true sentence about your own life ("Learning to drive was a steep learning curve for me"), because expressions anchored to real memories retrieve naturally under pressure. Second, cap the active set: ten expressions you can deploy flawlessly beat forty you half-know. Depth reads as fluency; breadth half-mastered reads as risk.

How many idioms do you need for band 7 or 8?

There is no quota, and thinking in quotas is the mistake. The examiner is not counting idioms; they are forming an impression of whether your vocabulary is flexible, precise, and natural. One well-placed it was a bit of a letdown contributes to that impression. Three proverbs in one Part 2 answer destroy it.

A realistic picture of a strong performance: phrasal verbs and collocations throughout, conversational chunks in most answers, perhaps two or three colourful expressions across the whole test — each arriving because the meaning called for it. If an idiom does not come to mind naturally in the moment, the correct move is to not use one. Accuracy and naturalness always outrank colour; that is consistent with how the Lexical Resource criterion is written, and you can read the official band descriptors for yourself at ielts.org.

The way to find out whether your idiomatic language is landing is to test it under pressure. Take a full IELTS speaking mock test and look at the Lexical Resource feedback specifically: if your less common vocabulary is being flagged as inaccurate or unnatural, cut your active set in half and drill what remains. And if you want the wider scoring context, the speaking band descriptors explained shows how idiomatic language fits alongside the other things the vocabulary criterion measures — it is one ingredient, not the recipe.