How to Read a Vernier (caliper)





Introduction: How to Read a Vernier (caliper)

Looking at an early caliper, you'll notice that it kinda looks like a tomahawk and has a scale down it's length. More about the scale later. On the bottom left, the "blade of the hatchet" are the jaws of the caliper for measuring outside dimensions - think of a tube. This would measure the outside diameter. The "pike" on top of the hatchet is used for measuring inside dimensions . Again, think of a tube's inside diameter. Looking all the way to the right...I know it's hard to see...but there's a little "tail" sticking out of the center of the handle. That will measure the depth of a step or some other similar feature. That little button on the top near the "pike" is a locking screw. The one just below it is a thumb button.

Step 1: Holding the Caliper

This is the proper way to hold a caliper. Use your thumb to slide the jaws open and closed. Yup, another tool that was totally designed for righties. Use the locking screw at the top if you want to set a dimension on the caliper and then check parts against your setting. Though it may not look it, the measurement between the inside and outside jaws are EXACTLY the same.

Step 2: Course Reading #1

So let's read a measurement off of the caliper.

First, a quick math refresher. Whole numbers (1,2,3, etc.) are followed by a decimal point and an endless number of zeros (2.000000). We are going to be working with the 3 places to the right of the decimal point. The first number to the right of the decimal point is a tenth of an inch (1/10), the second number signifies a hundreth of an inch (1/100), and the third number signifies a thousanth of an inch (1/1000). A human hair is about 3 thousands of an inch (0.003), give or take a thousanth. This number (0.456) is read as four hundred and fifty-six thousands.

If you noticed, the "handle" of the caliper has a scale that starts from zero on the left and goes up to 6 inches on the right, in this case. Other calipers can be much longer in length. The big number in the center of the scale is the inch number. In this case we are looking mostly at the area AFTER the first inch mark on the left, and then we see the number 2 on the right, which indicates the second full inch. Notice that each inch is divided into 10 equal parts with the numbers 1 through 9. That makes each one of those lengths 1/10 of an inch (0.100). And then each amount of space between each 1/10 of an inch has 3 lines - which breaks each 1/10 of an inch into 4 equal pieces. Each one of those little pieces, therefore, is twenty-five thousanths of an inch (0.025) long. There's also a scale on the bottom of the picture. It starts at zero, there's a 5, a 10 and a 15. It goes up to 25, but the image doesn't show that. THAT, is the vernier part of the caliper. Notice that the line for the 0 (zero) is to the right of the second line after the number 3. Since we know that there is a large number 1 to the left of the image that we can't see (which signifies 1 whole inch), let's write that down (1.) and we'll put the decimal point in. The 3 is to the left of the zero on the vernier, so we'll add that to our number (1.3). The zero line is to the right, of the second line after the 3. So there is at least fifty thousanths there (0.050), but there's more. Notice how the zero line is just a smidge to the right of that second line after the 3. Now look at the large 2 and notice that the vernier line of 13 is to the LEFT. So the trick is to find which lines on the vernier lines up exactly with the scale on the center. In this case, it looks like 6...but let's get a closer look.

Step 3: Fine Reading #1

Yup. It's 6 all right.
NOT the 6 on the top scale - the 6 on the bottom vernier scale.
So, we were up to 1.3, plus we knew we had at least another fifty thousanths (0.050), and the vernier tells us there is an addition six thousanths (0.006). Add them all up and we have 1.356 - read 1 inch, three hundred and fifty-six thousands.

Step 4: Course Reading #2

Let's try another one.

The zero on the vernier is to the left of the 1 whole inch the number is LESS THAN 1 full inch. Let's write that down (0.) and don't forget the decimal point.

We're between 6 and 7 on the 1/10 scale, so let's write that down too (0.6).

Hmmm, the vernier zero line is almost at the number 7; there are 3 lines...seventy-five thousanths (0.075) the left of the vernier zero line...and some more.

Let's look at the vernier scale and see what lines up to understand how much more.

16, 17, 18 - not sure. Let's get a better shot of that.

Step 5: Fine Reading #2

It looks like 15.

So, that's 0.6 plus 0.075 plus 0.015.

That would be 0.690.

Read, six hundred and ninty thousanths.



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    42 Discussions

    I've never seen a metric vernier caliper - only dial calipers. Though I imagine that they do exist and that they would work relatively the same.


    5 replies

    I just got one from Home Depot, it has both metric and standard readings, though the standard looks to be in fractions, not decimals, so I have next to no clue how to read it properly. The metric side, however, is easy to understand after your instructions (converting them to fit the metric scale, of course).

    .25=1/4=Quarter inch=6.2mm. Real easy to read.

    2.5cm=25.4mm=1 Inch
    Just some simple conversions for you all.


    2 years ago

    It's amazing how you guys like using the decimal point, but don't like using the decimal system! Millimeters make it much easier.

    6 replies

    Back in the 70's when we tried to trade in all of our American system calipers for decimal system calipers, there was going to be a sixpence fee.

    Because the American system of measurement sucks!

    There are 2 types of countries in this world. Those that use the metric system and those that have put a man on the moon

    ... and also crash a space probe (Mars Climate Orbiter) from mistake in unit conversion.

    Metric system is far simpler than Imperial system. You just move the decimal point forward or backwards to get you measurements. Add or take a zero. 30g=300mg, etc.

    hey i saw vernier caliper educational app and learn all about the vernier caliper. It illustrates the various parts of the vernier caliper and demonstrates how to use. It has a real time exercise to use the vernier caliper and practice the functions of it.see tis link

    I have a master's degree; I took a total of 7 years of math in high school and college. I made A's in English and reading comprehension. But I cannot follow these instructions. I have the cheap Harbor Freight calipers mentioned by a reader previously. They have different scales. I realize the principles would be the same but I don't understand what I am reading; I go back to the pictures but they aren't helpful. Annotating the pictures would be helpful so I know what they description is referring to. I'm not suggesting you do that since you put a lot of work into it. But I still am no closer to learning how to use these calipers than I was before.

    4 replies

    I understood well after reading few times. I was a high school drop out.

    Your brain is better developed than mine in the vernier caliper area : )

    I didn't have any problems understanding the instructions and I graduated from a community college.


    It appears that you have a very unusual caliper.
    But let's see what's going on here.

    On that central bar that doesn't move, you have 2 scales - one on top of the other...they both start at zero on the left. The bottom scale starts at zero, has divisions, and the first number is 10, then there's 20, and 30, etc. The top stationary scale starts at zero, there are some divisions an then there is a big 1, some more divisions and then a big 2. So it appears to me that the top scale is in inches and the bottom scale is metric. I know this because I also know that 1 inch equals 25.4 millimeters. If you look where the 1 on the top stationary scale coincides with the bottom stationary scale, you will see that it lines up with a number just past 25.

    OK. Let's test that. Look at the moving scale at the top...near the "pike". It start off with zero, there are 3 lines and the fourth line has a 4, three more lines and at the fourth line there is an 8. It says these are divisions of 1/128 in...but we'll get to that later. Line up the zero of that top moving scale with the 1 on the top stationary scale as exact as possible. Now look at the bottom moving scale that starts with zero at the left and every other division is increased by 1. I'll bet you, that while the zero on the top moving scale is lined up exactly with the 1 on the top stationary scale, that exactly at that moment the zero on the bottom moving scale is just a little bit to the right of the big line between the 20 and the 30 (that would be 25) on the bottom stationary scale. Additionally, the 4 on the bottom movable scale lines up exactly with one of the lines on the bottom stationary scale.

    Tell me how I did, and then we'll continue.
    You can write to me at

    I just found an on-line vernier caliper tutorial with a simulator you can adjust by dragging the jaw with your mouse. You can write your reading on a piece of paper and then click "show" to learn what the correct reading is to a tenth of a millimeter. I tried to link it through the rich text editor here, but it would not work, so here is the URL: