There is no shortage of "free IELTS practice tests" online. Most of them are recycled PDFs with no marking. Here is what separates a practice test that actually improves your band from one that just wastes an evening.
Reading and Listening have fixed correct answers, so a static PDF with an answer key is genuinely useful for them — as long as it is timed properly and scored against the real band-conversion tables, not a rough guess. Writing and Speaking are different: there is no answer key, because the "correct answer" is a judgement call about task achievement, coherence, vocabulary, and grammar. A practice test for those two skills is only as useful as the feedback attached to it — without that, you are just producing text into the void.
A good Reading or Listening practice test should be a full, unedited passage or recording — not a shortened excerpt — timed exactly as the real exam (60 minutes for Reading, roughly 30 minutes of audio for Listening), with a proper raw-score-to-band conversion table. Raw scores do not map to bands in a straight line: the exact conversion shifts slightly test to test, so a fixed "38/40 = band 9" rule of thumb from one source can be a little off on another.
This is where most "free practice test" sites fall short — they hand you a prompt and a timer, then nothing. You finish an essay with no idea whether it is a 5.5 or a 7.5, which is exactly the gap that leads people to over- or under-estimate themselves before the real exam. Look for practice that scores your response against the actual four IELTS Writing criteria (Task Achievement, Coherence and Cohesion, Lexical Resource, Grammatical Range and Accuracy) or the Speaking criteria (Fluency and Coherence, Lexical Resource, Grammatical Range and Accuracy, Pronunciation) — not a generic "grammar checker" score, which measures something different from what an IELTS examiner marks.
There is no magic number, but the honest answer is: enough that timing stops being the thing that trips you up. Most candidates underestimate how much the clock affects their score — running out of time on Reading passage 3, or writing a rushed 180-word Task 2 essay, costs more bands than most grammar mistakes do. Repetition under real timing conditions, with feedback on what to fix each time, matters more than the raw count of tests attempted.
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