Posted On Friday, 18. May 2012
(Are you an IELTS examiner? Is there anything in the following article that is inaccurate? Please let me know at: ryanthiggins@gmail.com.)
People are often confused by the methodology used to calculate the IELTS writing mark. As you know, your IELTS writing band is made up of your performance on two separate writing assignments, more commonly known as Task 1 and Task 2. But what you may not know is how these assignments are weighted against each other to formulate your overall writing band. Knowing the answer to this question gives the IELTS student a major advantage in the exam.

As was recently explained to me by former IELTS examiner Chris Green (of http://ielts-yasi.englishlab.net/), examiners first assign a band to each of a student’s tasks. Then the examiner uses a chart to calibrate precisely what the student’s overall writing band is. According to this chart, the Task 1 to Task 2 weighting ratio is about 1:2 (in other words, Task 1 contributes 33% and Task 2 66%).
Below you can see a copy of the chart (reproduced with permission from Chris Green at http://ielts-yasi.englishlab.net/). Please note that Chris was an examiner several years ago and created this chart based on what he estimates the current score chart to look like. Thus, it may not accurately reflect the numbers used by today’s active IELTS examiners (click the image to enlarge):

Knowing that Task 1 and Task 2 are weighted 1:2, some interesting observations can be made. For example, if you perform at a band 8 in your Task 1 response, but only receive band 5 for your Task 2, your writing will be labeled an overall band of 6. However, if these marks are reversed (that is to say your Task 1 is band 5 and your Task 2 is band 8), you will be honoured an overall band of 7. In fact, even if your Task 1 mark were to fall to a band 4, you would still be awarded an overall band of 7.
Let me summarize the above in a few quick equations:
Task 1 Band 8 + Task 2 Band 5 = Overall Writing Band 6
Task 1 Band 5 + Task 2 Band 8 = Overall Writing Band 7
Task 1 Band 4 + Task 2 Band 8 = Overall Writing Band 7
So what conclusions can we draw from this?
The above equations illustrate three things.
The first is that the 1:2 weighting ratio can shift slightly depending on the combination of marks you receive.
The second is that perhaps the best strategy a student can take is to engage Task 2 first, then proceed to Task 1. In doing this, the student prioritizes the Task 2 response, which heightens their chances of performing well in this area. This would in turn heighten their chances of receiving a higher overall writing band.
The third is just how important it is that you perform well on the Task 2 portion of the exam. I can tell you from my experience correcting Task 1 and 2 writing samples that students underestimate their abilities to engage Task 1 and overestimate their abilities to engage Task 2 (this is particularly true for students engaging the Academic exam). I believe this is why many students are surprised by how low their writing mark is.
If you are one of these people, my guess is that your Task 2 is weak and the additional weight this Task contributes to your overall mark is causing the depression you see in your writing band. As the above examples show, a strong Task 2 can overshadow a weak Task 1. It is thus imperative that you have your writing checked at least once by a native English speaker before you engage the IELTS.
So I hope the above both clears up any confusion you had regarding how this section is marked and helps you strategize a personal plan for your writing.
Be sure to check out the other resources at Chris’s website, too. There are lots of speaking resources and an interesting section that makes an educated guess for upcoming exam topics: http://ielts-yasi.englishlab.net/