How to Use This Tool
Enter your four section scores and your target. The tool works out which single section, improved by the smallest amount, actually changes your overall band.
Why subtraction gives the wrong answer
The IELTS overall band is not four hurdles. It is the mean of the four sections, rounded to the nearest half band. That rounding is what makes the obvious approach fail.
Take L 6.5, R 6.0, W 5.5, S 6.5. The average is 6.125, which rounds down to 6.0. Writing is clearly the weakest section, so it looks like the place to work. But raising any section by half a band takes the average to 6.25, which rounds up to 6.5. The weakest section is not special; the distance to the next boundary is doing all the work.
Now shift the starting point slightly: L 6.0, R 6.0, W 5.5, S 6.0 averages 5.875, which rounds to 6.0. Here the picture inverts. Half a band anywhere lifts the average to 6.0 — still band 6.0. A full band in one section reaches 6.125, which is still 6.0. Half a band in two different sections also reaches 6.125, and is still 6.0.
To clear 6.25 from 5.875 you need the average to rise by 0.375, which is three half-band steps spread however you like. From 6.125 it was one step; from 5.875 it is three. Those two starting points differ by a quarter of a band and the work between them differs threefold, which is not something subtracting your weakest section from your target could ever surface.
The rounding rule, exactly
IELTS rounds the mean to the nearest half band, and the two edge cases both round up:
- An average ending in .25 rounds up to the next half band. 6.25 becomes 6.5.
- An average ending in .75 rounds up to the next whole band. 6.75 becomes 7.0.
- Anything below .25 rounds down to the whole band; between .25 and .75 it lands on the half.
Because there are four sections, the mean can only end in .00, .125, .25, .375, .50, .625, .75 or .875. Half a band in one section moves the mean by exactly 0.125, which is why single-section improvements so often land just short of a boundary.
Section minimums are a separate constraint
Many universities set an overall band and a floor for every section. Those two conditions do not interact: a section below the floor has to be raised whether or not doing so moves your overall band. The tool lists those separately, because they are the improvements you have no choice about.
