Accurate to 0.5 at best, 1.0 is closer to the truth
I had high hopes for these pH test strips because they claim 0.25 increments.  However, these increments are not as rigorous in practice as they would appear in the diagrams.  Indeed, when I used these strips to assign the pH of my pool, and compared the results with a calibrated pH meter, I was usually off by 0.5 - 1.0 units.  So the 0.25 increment is wishful thinking.  But there are regions in the pH scale where these strips are more sensitive than others, as they rely on indicator dyes which have sharp color transitions at some pH points.  That said, there are also regions where it is difficult to be accurate to ±1.5 units.
Rating: 3 stars