Picture of 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.
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Step 1: Holding the caliper

Picture of 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.

Thanks for the great refresher! I hadn't used my vernier in several years and was really rusty when I tried to use it. The pictures and text were great, they brought me right back up to speed so I can now reload with confidence. My vernier is an older Craftsman and has both inch and metric scales.

bethegan25 days ago

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.

blackslax (author)  bethegan25 days ago

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
Herber4 months ago

Thanks that was an excellent review.

depotdevoid2 years ago
Thanks for this, I've come back to it several times since I found an old vernier in my desk here at work. Using your instructions, it's more accurate than the dial and digital calipers, and doesn't go out of whack over time. Very useful when dealing with bearings!
blackslax (author)  depotdevoid2 years ago
Thanks for the comment Depotdevoid.
Users like yourself is exactly why I wrote the instructable.
And the one thing I like about the (old fashioned) vernier is that they are far more durable than the dial calipers. Drop that dial caliper once and your chances are 50-50 that its a goner.
Phil B3 years ago
Thank you for this. I think I will need to look at it a few more times. I looked at a vernier caliper and considered buying it a few months ago. I was having some trouble understanding it. Your explanation helps. Not much later I received some gift money and bought a digital caliper. It may be cheating, but it sure is easy.
blackslax (author)  Phil B3 years ago
It's not cheating.
That's like saying it's cheating using a level instead of a clear plasstic tube and water.
There's no question about it - dial calipers and digital calipers are easier to use - especially for those of us that remember the Beatles.

I do remember the Beatles, which means I also remember The Ed Sullivan Show.
I bought a digital caliper and the thing never reads anywhere near a useful measurement, it's all in 1/128 and 1/64's I don't need to be anywhere near that accurate.
My digital caliper reads in decimals, not fractions. I can convert to fractions on a slide rule or a calculator. My caliper also gives me the option of metric or English readings.
amchaffie3 years ago
Fantastic explanation, I never really understood how to read off the smaller figures, Now hows about a metric one for us Brits :)
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:
blackslax (author)  Phil B3 years ago
I would think that the Java is what is messing it up.

blackslax (author)  amchaffie3 years ago
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.

Eye Poker3 years ago
I bought a cheap plastic caliper from Harbor freight and it gets more use than most tools in my shop.
blackslax (author)  Eye Poker3 years ago
Yea, even a cheap plastic vernier caliper can give you some pretty good results. Just don't try to measure any freshly cut metals.

rimar20003 years ago
Very interesting instructive. It amazes me that almost nobody knows check read a vernier!
blackslax (author)  rimar20003 years ago
Well, when you have dial calipers and digital calipers available, the vernier caliper gets overlooked. The best part about the vernier caliper is that it can last forever. I've seen dial calipers have their dial come off and of course - digitals need batteries. Not very sustainable.

jdege3 years ago
It's nice to see some closeups that are actually in focus. It's all too rare, here.
blackslax (author)  jdege3 years ago

I had to go through 4 or 5 close-ups to get these.
They say a picture is worht a thousand words...but not blurry pictures.