Short answer: A range of complex sentences is half of your Grammatical Range and Accuracy score, which is worth 25% of both your Writing and Speaking bands.
Band 7 rewards varied complex structures produced accurately - not the longest or rarest grammar - so aim to mix simple, compound and complex sentences and keep the complex ones under control.
Most candidates who plateau at Band 6 or 6.5 can already write a complex sentence; what they lack is range used accurately. They repeat the same one or two patterns, or they reach for tangled constructions that collapse under their own weight.
This guide is narrower than our broad grammar for Band 7 guide: it is only about sentence structure - how to build variety, where subordination and relative clauses earn the most marks, and how to add complexity without sacrificing the accuracy that caps your band.
What "range of structures" means for Band 7
Grammatical Range and Accuracy (GRA) is one of the four equally weighted criteria in Writing and one of the four in Speaking, so it is a full 25% of each band.
The name splits the mark in two: range is the variety of structures you can produce, and accuracy is how correctly you produce them. Sentence variety - simple, compound and complex forms used naturally - is the visible core of range.
For how all four criteria combine into your overall band, see how IELTS Writing is scored.
The official descriptors make the target concrete.
Band 6 "uses a mix of simple and complex sentence forms" and "makes some errors in grammar and punctuation" that "rarely reduce communication"; Band 7 "uses a variety of complex structures" and "produces frequent error-free sentences"; Band 8 "uses a wide range of structures" with the majority error-free.
Read them side by side on the IELTS.org Writing Task 2 band descriptors and the lesson is clear: Band 6 and Band 7 candidates both attempt complex sentences - the difference is how many come out clean.
Range is not about length or exotic grammar; it is about variety kept accurate.
The same criterion applies in Speaking, where the examiner listens for exactly the same variety - a candidate who speaks only in short, simple statements is capped just as a writer would be.
Speech tolerates a little more looseness, but the principle is identical: show that you can subordinate one idea to another and vary your sentence shapes.
Everything in this guide therefore lifts both scores at once, which is why sentence variety is one of the most efficient things you can drill.
Simple vs compound vs complex sentences
Three sentence types give you all the variety Band 7 asks for.
A simple sentence has one independent clause: Automation raises productivity. A compound sentence joins two independent clauses with a coordinating conjunction (and, but, so, yet) and a comma: Automation raises productivity, but it displaces workers. A complex sentence joins an independent clause to a subordinate clause using a subordinator (although, because, while, if, since): Although automation raises productivity, it displaces workers.
Range means moving between all three on the page, not writing fifteen complex sentences in a row. A strong paragraph typically opens with a clear topic sentence, develops the idea with complex and compound sentences, and lands on a short simple sentence for emphasis.
The table below shows each pattern, a correct example, and the error that most often turns it into a lost accuracy mark.
| Sentence type / pattern | Correct example | Common error |
|---|---|---|
| Simple (one independent clause) | Automation raises productivity. | Writing only simple sentences, so no range is shown. |
| Compound (two clauses + coordinator) | Automation raises productivity, but it displaces workers. | Comma splice: joining the two clauses with only a comma. |
| Complex (independent + subordinate) | Although automation raises productivity, it displaces workers. | Fragment: leaving the subordinate clause standing alone. |
| Complex with defining relative clause | Workers who lack training are displaced first. | Adding commas to a defining clause and changing the meaning. |
| Complex, front-loaded subordinate clause | While critics warn of job losses, firms keep automating. | Forgetting the comma after a front-loaded clause. |
The two errors worth memorising are the comma splice - joining two independent clauses with only a comma, as in Costs fell, demand rose - and the fragment, where a subordinate clause is punctuated as a full sentence, as in Although costs fell. Both are frequent, both are easy to see once you look for them, and both pull an otherwise ambitious sentence down into Band 6 territory.
A useful way to feel the difference is to notice what each type does. Simple sentences state a fact cleanly and are perfect for a punchy claim or a definition. Compound sentences balance two equal ideas - a point and its contrast, or a cause and its result.
Complex sentences subordinate one idea to another, which is where analysis lives, because analysis is largely about showing how ideas depend on each other.
A Band 7 answer leans on complex sentences for its arguments but never abandons the other two; the variety itself is part of the mark.
Relative clauses and subordination
Subordination is the engine of range because it lets you show the relationship between two ideas - contrast, cause, condition, time - inside a single controlled sentence.
Vary the subordinators you use (although, whereas, because, since, while, if, unless, even though) and vary where the subordinate clause sits.
Front-load it in one sentence - While critics warn of job losses, firms keep automating - and put it second in the next - Firms keep automating, even though critics warn of job losses. That flexibility is exactly what a Band 7 answer looks like on the page.
Relative clauses are the lowest-risk range marker of all.
A defining relative clause identifies which noun you mean and takes no commas: Workers who lack training are displaced first. A non-defining clause adds extra, non-essential information and is fenced with commas: Retraining schemes, which many governments now fund, ease the transition. Two accuracy rules protect the marks: use that only in defining clauses and never after a comma, and do not use which to refer loosely to a whole preceding clause.
For the wider set of high-value structures beyond sentence shape, our Band 7 grammar guide covers conditionals, the passive and participle clauses.
Two more relative pronouns widen the range further. Use whose for possession - families whose income falls below the line - and where for a place or situation - a system where costs are hidden.
You can also reduce a relative clause to a participle for a more compact, advanced feel: the workers who are affected becomes the workers affected, and a report which was written last year becomes a report written last year.
Reductions read as controlled and save words, but only reduce a clause once the full version is already accurate.
Complexity without losing accuracy
The most common self-inflicted wound at this level is chasing complexity for its own sake: stacking three subordinate clauses, reaching for tenses you cannot control, and producing a sentence the examiner has to read twice. The descriptors never reward length - they reward error-free sentences.
A clear, correct complex sentence beats an ambitious one that collapses, every single time.
Here is the trap in action.
A candidate trying to impress writes: Although it is true that, despite the fact that automation, which many economists study, raises productivity, it displaces workers who, because they lack training, cannot easily be re-employed. The examiner has to untangle it, and the errors multiply along the way.
The controlled version says the same thing in two clean sentences: Although automation raises productivity, it displaces low-skilled workers. Because these workers lack training, they cannot easily find new jobs. Same ideas, two accurate complex sentences, a clearly higher band.
The practical rule is to write within your control while steadily widening what you control. If a sentence has grown to three or four clauses, split it in two.
If you are unsure whether a structure is correct, choose the version you can produce accurately, then practise the harder version separately until it too becomes reliable. Range should grow out of security, not replace it.
In Task 2 especially, this discipline pairs with clear paragraphing - see our Task 2 structure guide - so that varied sentences sit inside a well-organised argument rather than compensating for a messy one.
A worked before/after
The paragraph below was written for this article as a teaching example - it is not taken from any real test. It shows a Band 6-style answer rewritten to Band 7 by adding sentence variety and fixing accuracy, without adding length or rare grammar.
Before (Band 6): Many people use cars. Cars cause pollution. The government should build more public transport, this will reduce pollution. Public transport is cheap it helps people who cannot drive.
Three problems: every sentence is simple, there is a comma splice (...public transport, this will reduce...), and there is a fused sentence (cheap it helps). The ideas are fine, but the structure is flat and the punctuation leaks marks.
After (Band 7): Because so many people rely on cars, pollution has risen sharply in most cities. If governments invested in public transport, emissions would fall - and the systems they built would also help people who cannot drive. Affordable transport, which serves commuters and non-drivers alike, is therefore both an environmental and a social solution.
Notice what changed. The rewrite mixes a complex sentence (Because...), a conditional (If... would), and a sentence with a non-defining relative clause (which serves...).
It varies where the subordinate clause sits, replaces the comma splice with proper subordination, and fixes the fused sentence. No word is rarer than in the original - the band rose because the structure became varied and the punctuation became accurate.
Run your own paragraphs through the Writing Checker to see which sentences a marker would flag and how a rewrite lifts the estimate.
How to build the habit
Range is a habit, not a fact you memorise the night before. Build it in small, daily reps. Take one idea and write it three ways - as a simple sentence, a compound sentence, and a complex sentence - until switching between them is automatic.
Keep a personal list of five or six subordinators and rotate them, so you are not opening every sentence with because. Read one short model answer a day and underline every subordinate and relative clause; noticing the pattern in strong writing trains you to reproduce it.
Then get feedback, because you cannot see your own comma splices. The IELTSbiz Writing Checker scores an essay against the four criteria and flags grammar errors sentence by sentence, so you learn whether your GRA is capped by a lack of range or by repeated slips.
A daily habit with the Word Coach keeps you writing accurate sentences every day, and the broader grammar for Band 7 guide gives you the next structures to add once your sentence variety is secure.
Give the habit a weekly focus, too. Spend one week deliberately overusing relative clauses until they feel natural, the next varying your sentence openings, the next hunting comma splices in your own drafts.
Narrow, rotating goals beat a vague intention to write better, because each one leaves a concrete skill behind. Over a month, the four or five structures that separate Band 6 from Band 7 stop being things you remember to use and become the way you naturally write.
Conclusion
Band 7 sentence variety is not about long or exotic grammar; it is about mixing simple, compound and complex forms and keeping the complex ones accurate.
Vary your subordinators and where the subordinate clause sits, use relative clauses as your low-risk range marker, and split any sentence that has grown out of control.
Build the habit with daily reps and honest feedback, and the "range of structures" the descriptors ask for becomes something you produce without thinking.