If you want to measure with greater accuracy than a ruler, a dial caliper is an easy-to-use, versatile, and relatively budget-friendly tool. You can use it to measure outside widths or diameters, internal dimensions, and the depths of steps or holes.
While models tend to look similar, there are important differences you need to consider, so we’ve put together this concise buyer’s guide. At the end, you’ll find a few reviews of our favorites. Our top choice, the Anytime Tools 6-Inch Dial Caliper, is a high-quality, feature-rich tool that’s accurate enough for the pro yet remains affordable for the home user.
With digital calipers widely available, you might well ask why you’d choose a mechanical dial model. There are several reasons. First, you’ve no need for batteries (which always go dead when least convenient). Second, a dial caliper is easy to calibrate. Third, they’re generally more durable and less susceptible to environmental conditions (heat, water, magnetic fields, etc.). If you need absolute accuracy — in scientific measuring, for example — then digital is the way to go. Some can measure to 0.0005 inch. You’ll need deep pockets though!
Dial calipers are usually rated by the maximum size they can measure. Six inches is the most common, but there are 8- , 12- , 18- and 24-inch dial calipers available.
The most important issue for most people is precision, and it’s vital to understand the difference between resolution and accuracy. Resolution relates to the markings on the dial. Most will be marked to 0.001 inch and/or 0.20 millimeter. Be careful though, anyone can print small increments. Actually making the tool that accurate is much more difficult.
When a gear wheel runs along a toothed slide (which is basically how a dial caliper works), the teeth don’t mesh perfectly. On quality tools, it’s very close, but less so on cheap versions. That looseness or “play” is called backlash. The more you have, the less accurate the tool. Some manufacturers claim their accuracy is the same as their resolution, but in practice it’s seldom the case. The makers of the best high-end dial calipers will quote resolution of 0.001 inch, but accuracy of 0.002 inch. In general, we’d say most midrange models will have a repeatable accuracy of between .005 inch and .01 inch. That will be plenty good enough for many, but, of course, it depends on the application.
While there are a few fiberglass and plastic models around, most are made of stainless steel, which is more durable and highly resistant to rust. It’s worth checking the legibility of the dial — some can be a bit confusing. Most are marked with decimal numbers, but fractions are also available, which some people prefer. You’ll also find some have both imperial and metric scales, where others have one or the other.
Dial calipers don’t do well if knocked or dropped, and there’s little you can do if it gets bent. Some are sold as shockproof. It can help with minor impacts, but there’s a limit to the protection it offers.
You can find a cheap dial caliper for around $20. For home engineering and automotive enthusiasts who are okay with less precision, they’re fine. They might claim 0.001-inch accuracy, but don’t expect that consistently. Most tools of a professional standard cost between $35-$50 for 6-inch versions, whereas 12-inch and larger models will easily double or triple that price.
A. A regular wipe down with rubbing alcohol should remove most dirt. You can also use compressed air. If you find it’s not sliding freely you may need to disassemble, but it’s not complicated. Lubricate after with light tool oil or silicone oil. Do not use petroleum-based oils (like WD-40). The sticky residue will pick up more dirt.
A. It’s the Society of Automotive Engineers, set up in 1905 by Henry Ford and Andrew Ricker. Today, it sets standards for measurement, among other things. If you see SAE on a dial caliper, wrench, sockets, etc., it means they use the US measurement system (feet and inches) rather than metric (millimeters).
Anytime Tools’ Six-Inch Dial Caliper
What you should know: Accurate, durable, yet affordable tool for both amateur and professional users.
What you'll love: Dual scales — inches and millimeters — with black or red markings and needles for easy identification. Shockproof stainless steel construction, with anti-backlash springs. Reads to 0.001 inch / 0.020 millimeter.
What you should consider: A few owners have had problems with inconsistent zeroing.
Where to buy: Sold by Amazon
SE’s Six-Inch SAE Dial Caliper
What you should know: Practical, low-cost tool for the home engineer or mechanic.
What you'll love: All the important features at a budget-friendly price. Inside, outside and depth measurements. Stainless steel body with clear dial showing 0.001-inch increments.
What you should consider: Only measures in inches. Sometimes requires adjustment and lubrication on arrival.
Where to buy: Sold by Amazon
Shop Fox’s Fractional Dial Caliper
What you should know: High-quality tool from an engineering brand known for durability and value.
What you'll love: Some people prefer to read fractions, and this six-inch model gives fast, consistent results in 1/64-inch increments. Numerical measurements also provided in 0.01-inch steps.
What you should consider: It’s at the top end of what you’d expect to pay.
Where to buy: Sold by Amazon
Sign up here to receive the BestReviews weekly newsletter for useful advice on new products and noteworthy deals.
Bob Beacham writes for BestReviews. BestReviews has helped millions of consumers simplify their purchasing decisions, saving them time and money.
