Reading a ruler measurement requires being very accurate and observant about the fractions of inches and centimeters, and guesswork is often necessary to get an exact decimal measurement. Read a ruler, whether it be metric or in inches, with an online math lesson from an experienced high school teacher in this free video on mathematics.

## Video transcription

Hi, I'm Steve Jones, and I am going to tell you how to read a ruler measurement. The most important thing about the ruler, is it is on your tool, and it is only as accurate as you are, when you use it. I'm giving you an example here. We've got a book, and the book as you can see, is a certain length, but the most important point is this one, that if you're going to measure with a ruler, you make sure that the end of your book is exactly in line with the zero, on your ruler. This ruler is metric, that is it has ten divisions, between the individual numbers. Now, whether you're working with inches, or with centimeters, very often they are calibrated in tenths, even tenths of inches rather than in eighths, or sixteenths, unless you are working in industry, so here we have to have it exactly on the zero. Well, as exact as you can be. The other end of the ruler then, we can see that on the scale, we have reached the point, and here is our end point. This is the important point, our end point, and that end point, if you can see, is between 8 and 9, so it's between 8 and 9, so you know that the length is between 8 and 9, which means that the answer is going to be, 8. something, because if it was 9. something, it would be more than 9. It would be at this side. Now, if you look at the smaller measures, you can see that there are one, two, small divisions, so this is 8 here. This is 8, 8.1, 8.2, so I can put .2, because that is the second marker. Now, there's .3, but it's less than .3, and now comes a little bit of guessing. You have got to be really clever. You now have to look and see, well, is it nearer this one, is it nearer that one? Between these two markers that I've put a dot on, here they are. This is 8.2, and this is 8.3, and this is the edge of the ruler. We can see that it's actually coming, say here somewhere, so you've got to imagine ten little spaces here, and one, two, three, four, five, about five, six, something like that, so you estimate the last number, so 8.26, whatever units, so the thing that we have to remember with this, this is not the ruler that's doing the measuring, it is you that is doing the measuring. The ruler helps you, but if you do this part wrong, then your measurement is wrong, or should we say, your measurement is going to be inaccurate, so if you do this part correctly, this accurate measurement, guessing, because that's what it is, is a guess. If you do that correctly, you will end up with the best measurement you can get, and that is the best way to do a ruler measurement.