Calipers are precision instruments used to measure physical dimensions, often inside measurements, outside measurements, or depths.
Micrometers are similar, but are often configured for more specific measurement types, such as only measuring outside dimensions or only inside dimensions. Micrometer jaws are often specialized.
For instance, these are inside micrometers, meant for measuring the distance between two points. Outside micrometers measure the thickness or width of an object, while inside micrometers typically measure the space between two points. These inside micrometers might be used for measuring the width of a hole or slot, for example.
What are some differences?
Following are some generalizations that I’ve found to be true over the years. There might be other differences, or some of these differences might not apply to all applications.
To start, micrometers are often more accurate.
My Mitutoyo 6″ digital calipers, for example, are accurate to ±0.001″, and with 0.0005″ resolution. My Mitutoyo digital micrometers are accurate to ±0.00005″, and with 0.00005″ resolution. That’s a difference of ±1/1,000 of an inch accuracy compared to ±1/20,000 of an inch.
What this means is that a caliper measurement of 0.500″ could be considered to be within 0.499″ and 0.501″, and a micrometer measurement of 0.50000″ could be considered to be between 0.49995″ and 0.50005″, if there are no other errors or uncertainties.
Ease of Use
Calipers are generally easier to use. Micrometers, on the other hand, require more finesse. If you’re not careful with micrometers, measuring the same thing 5 different times could result in 5 different measurements.
There are different types of thimbles, such as plain, friction, and ratcheting, that help with repeatability and the “feel” of taking measurements.
In high precision work, even the temperature of micrometers can influence measured values in a small way. That’s why some micrometers have insulated pads, to help reduce heat transfer from the user’s hands. There are also micrometer stands.
Micrometers, despite requiring more finesse, can be easier to use for measuring certain things, due to the smaller size of their jaws compared to calipers’.
With calipers, you can use the jaws for light marking tasks. Doing so can wear or blunt the jaws over time, and so it’s not necessarily something you want to do, but it’s something you can do. Micrometers can only be used for taking measurements. And, as mentioned, calipers can often be used to make different kinds of measurements (inner dimensions, outer dimensions, depths), while micrometers are usually singular-task tools.
Calipers and micrometers are both available with different styles and shapes of jaws. Ball micrometers, for example, are often used to measure the thickness of curved parts, such as pipe walls.
There’s something called offset centerline calipers, for example, with specially tapered jaws for measuring the center-to-center distances between holes. You can also find attachments for use with standard caliper jaws.
There are many different styles of calipers and micrometers, as well as some attachments, should your needs require them.
Calipers often have a wide measurement range, such as 0-6″. Calipers are available in other sizes as well, such as 0-4″, and 0-12″. Micrometer measurement ranges are a lot smaller, such as 0-1″. If you want to cover the entire range between 0 to 6″, you need a 0 to 6″ set, which comes with 0-1″, 1″-2″, 2″-3″, 3″-4″, 4″-5″, and 5″-6″ sizes.
Use in Other Equipment
You can find caliper-type and micrometer-type gauges in other equipment. A digital caliper-like scale might serve as a height gauge for a planer, drill press, or mill, and a micrometer-like scale might be found in the stage adjustment of a microscope or other inspection tool.
When to use one over the other?
Do you need to make quick measurements? Or is higher accuracy more important? Are you measuring objects of widely different sizes?
Calipers are good to start with, especially if you’ve been using a ruler or tape measure for all your measurements. Micrometers are more of a “you’ll know if you need it” kind of tool.
Which to buy?
Right now, the least expensive calipers I could recommend are plastic pocket calipers with a 0-3″ measurement range and 1/32″ or 1mm markings. They can be found for $10-12. They’re not as versatile as standard 0-6″ calipers, but they’re handy and can help you determine if you should budget for standard calipers.
Or you could buy some cheap no-name calipers, but these pocket calipers will still be handy after you upgrade.
Buy Now(via Amazon)
Buy Now(via Lee Valley)
See Also: Reader Recommendations for Inexpensive Digital Calipers
Readers recommended some mid-level brands for when you need something better than cheap no-name brands, but less expensive than industrial brands such as Mitutoyo, Brown & Sharpe, and Starrett. More budget-friendly industrial brands include SPI and Fowler.
You can find better brands of calipers for around $75 and up. Analog calipers (vernier or dial) are usually less expensive than digital.
Analog calipers are great for a lot of things, but can require practice and care to read. And good eyes, in the case of vernier calipers.
In this photo, the measurement of the barrel plug is… ~0.215, maybe 0.216″. Or ~5.50mm if reading the metric scale. I use my vernier calipers for certain things, but quick and easy measurements isn’t one of them.
See Also: Mitutoyo Vernier Calipers
See Also: Mitutoyo Digital Calipers Recommendation
Mitutoyo 0-6″ digital calipers can be found for ~$125 and up. These are my go-to’s, along with Mitutoyo dial calipers I also picked up on sale. Digital batteries require a coin cell battery, except for solar calipers like Mitutoyo’s, and eventually need to be replaced.
Buy Now(via Amazon)
Buy Now(via Zoro)
For micrometers, I like Mitutoyo’s 293-340, which has a ratchet stop.
Buy Now(via Amazon)
Buy Now(via Zoro)
For tools like these, I very much prefer ordering from industrial suppliers, such as MSC and Zoro. I bought several of my Mitutoyo tools from Amazon, but that was a few years ago. I’ve heard about counterfeits in recent years, which makes me hesitant.
Did I miss anything?
Did I leave anything out, or do you have your own usage tips to share?
In the first paragraph under Accuracy, shouldn’t that be calibers first?
Thanks! I checked and rechecked the numbers, and proofread several times, and I still messed up! First mistake of the new year! *Fixed it.*
Don’t worry, Darrin made the second mistake 🙂
I bought one of those LongLife Pocket Calipers from Lee Valley just to keep in my apron pocket. I have Vernier, Dial and Digital calipers but these are small enough to keep on hand and I use them for ‘give or take’ measurements such as working out what size drill bit to use for a wall anchor/plug.
Calipers are great for quick measurements. Micrometers are a must for engine building.
Bottom line, if you didn’t know what micrometers were before this post, you very likely do not need that level of precision
Very well said!
Was watching a YouTube tutorial on a 4wheeler carburetor diaphragm adjustment.
The poster stated if you could not remove the seat without help,you shouldn’t be working on a carburetor lol.
What do you think of dial calipers? They are my favorite to use because they are much easier to read than vernieer calipers and don’t require a battery to work.
Agreed. Even though I have a nice set of Mitutoyo digital calipers, I find myself using my dial calipers (fractional inch) more often. For woodworking I don’t need to go to the third decimal. Mine is from igaging and has an inside scale of 100ths and an outside scale o fractions. Which makes it a lot easier to round up to the next 16th or 32nds of an inch without having to memorize/calculate or refer to a chart. Even though many digital calipers let you hit a button to switch to fractions, I find too often that it goes to 128 or 64th which may be to granular for my need.
This link is for the igaging model that has both fractions and decimals.
30 buck at amazon. not the cheapest, but not so pricey that I am afraid to use it and keep it on the bench.
Dial calipers are a good balance between vernier and digital calipers. I like them for visualizations. That’s also why dial and test indicators have dial gauges, because they can show variations more visually than absolute measurements.
I bought a blue-faced Mitutoyo when it was on sale, and liked it so much I bought a second one.
It’s available at Amazon, but I bought mine from Enco and then MSC. The sale price was $72.
Good post, Stuart.
For inside measurements with a traditional set of micrometers, I’ve always used a set of telescoping gages. Again, though, you have to be very careful in order to get consistent measurements.
Small hole gages and telescoping gages are also useful, but sometimes inside micrometers can be easier and quicker to use. Price-wise, inside mic’s can cost less. But, gages have greater depth, and can access holes in recesses or beneath obstructions.
There are also bore gauges;
They’re too big to fit.
I checked, and even small hole gauges only go down to 1/8″. Barrel jack pin receptacles can be 2.1mm or even smaller. With small hole gauges starting at 3.175mm, they can’t be used to differentiate between say 5.5mm x 2.1mm barrel connectors, and 5.5mm x 2.5mm.
Yep – I plopped my comment down in the wrong spot. Bore gauges seem to be popular among engine builders – useless for barrel jacks.
So, those coaxial power connectors (as pictured) are always near impossible to figure out. Yes, the outer diameter is always easy, but that inner diameter – how does one measure that?
I do truly hope you give an answer that makes me feel dumb, but so far, I don’t know how to properly get that measurement. And those connectors already make me feel dumb because of that, so NBD…
If it’s something you come across a lot, maybe a set of go/no-go gauges consisting of plugs or jacks of known specs purchased from a supplier.
Or, go/no-go gauges using slightly undersized drill bits, round stock, or pins?
Barrel jacks are indeed incredibly frustrating to size.
I have a rechargeable flashlight with barrel plug, but no charger. So I ordered a “universal” one from Amazon. Not a single one of the tip attachments worked.
Even with a set of trial plugs & jacks, that’s not usually a viable thing – as you probably noticed, just because a plug fits into a jack physically doesn’t also mean that there’s connectivity in there. Guessing about voltage & AC/DC doesn’t always trigger a magic green light either.
Using a silver Sharpie or a P-Touch labeler religiously on wall-warts is the best insurance so far to keep things matched up, but once something goes missing…
In a sane world, those connectors would not be used.
To measure a barrel jack socket on a product, use something soft and impressionable like silly putty and gently push it on the socket. Don’t push it so hard that it fills the socket, you just want a little bulge, so that when you remove it, you can easily measure the outside of the bulge which will be the outer diameter of the plug, and the inner indent, which will be the size of the pin.
Mitutoyo. Understood. When my Lee Valley blindman’s Digital Caliper ceases to do the job, I will invest in Mitutoyo Calipers and a Micrometer as my next replacement.
You already got me to invest in the Klien 1019 Curve Crimper/Stripper, I’ll be damned if I’m going to quit trusting you for upgrade advice now.
You, Stuart, are now a primary source of great upgrade advice for me. It always works out. It’s You and Adam Savage on Tested really testing my endurance for what I know about a lot of these tools.
Even though the stated accuracy of (high quality) calipers is .001″, I like to measure anything I need closer than .003″ with a mic. This is because of the Abbe Error in calipers works against accurate measurement, and-especially in-situ on a lathe or mill- getting a “feel” for measurement force is often difficult. With a ratchet thimble mic, as long as I ratchet it with close to the same speed, I can be assured I am within .0002-.0004″ of the target measurement.
Great point, thank you!
Interesting, but, wow. Narcissism of minor differences comes to mind. Oh sure, not a big deal, just a world war, 20 million dead…um…oh what, yeah, both work fine.
Curious that you’re criticizing this site for explaining the difference between these tools, and yet you’re hear reading it rather doing something to save the world. Maybe better to worry about your own priorities rather than ours?
…Wait… Huh? I know Stuart doesn’t want Politics here, but I would GENUINELY like to know where Paul K pulled this comment from. What does World War II have to do with Calipers and Micrometers? Last I checked, and I admit it has been a while, MY Calipers have the markings for both Imperial AND Metric, with a little button on the digital component to cycle through Decimal Inch, Fractional Inch, and Metric Millimeter readings.
Frankly, if I want to replace my Calipers with a set of Mitutoyo higher end Calipers and a Micrometer… They’re going to have to have that same function, because I tend to work in Metric. All of this is very basic common sense stuff, so I KNOW Paul K wasn’t talking about Thousandths of an Inch versus Millimeter or Metric measurements on a Caliper or Micrometer…
Now… If we’re trying to say Every Micrometer is a Caliper, but not all Calipers are Micrometers, I would understand that… Every Truck is an Automobile, but not every Automobile is a Truck… But then… What does that have to do with the Death Toll of World War II?
I know this is mean to say, but… Paul? Were you Drunk when you posted that, by chance?