Micrometer vs Caliper: What's the Difference?

Micrometers and calipers are measuring instruments used for various applications, ranging from laboratories to factories.

These devices are generally used for measuring linear dimensions of workpieces with high accuracy.

But how exactly do these instruments differ, and what applications are they suited for?

The difference between a micrometer and a caliper lies in their range and accuracy. Micrometers offer a measuring range of around 0"to 6", whereas calipers offer a 0" to 2" range. Micrometers offer a measuring accuracy of up to 0.0004" while calipers have a comparatively lower accuracy of up to 0.0007".

This article will help you understand the differences between micrometers and calipers, how to choose one among the two, and the difference between their digital and manual variants. 

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Difference Between a Micrometer and a Caliper

Parameter	Micrometer	Caliper
Accuracy	More accurate	Comparatively less accurate
Range	Low range	Can measure a larger range
Functionality	Comparatively less	Single device can measure inner, outer, and depth dimensions
Ease of use	3 scales make it complex	2 scales make it comparatively easier to use
Cost	Comparatively high	Comparatively low

Micrometers and calipers are measuring instruments commonly used for precisely measuring linear dimensions.

However, they differ in various aspects, such as accuracy, measuring range, method of use, applications, parts, costs, and categorization.

After properly fastening the object, you can use either of these tools to measure length, thickness, diameter, etc.

Difference in Accuracy/Precision

Generally, micrometers give a more accurate reading compared to calipers.

Manual vernier calipers usually have an accuracy of 0.02 mm (0.0007 in) to 0.1 mm (0.004 in), whereas digital versions have an accuracy of 0.01 mm (0.0004 in).

Contrarily, manual micrometers generally have an accuracy of 0.01 mm (0.0004 in), with digital models having resolutions of around 0.003 mm (0.00012 in). 

Some advanced micrometers, such as the Mitutoyo Digimatic series, possess a resolution of 0.0001 mm (4e-6 in).

This difference can be better understood by an example.

If a micrometer measures the width of a wooden block to be 10.47 mm (0.412 in), calipers will show a reading of 10.5 mm (0.413 in). 

Difference in Range

Normally, calipers have a broader measuring range compared to micrometers.

Micrometers are usually available in measuring ranges of 25 mm (1"), starting from 0-25 mm (0"-1"), then 25 to 50 mm (1"-2"), and so on.

On the other hand, calipers usually have a measuring range of over 150 mm (6").

However, some large-size variants can even have ranges of 0-300 mm (0"-12") or 0-600 mm (0"-24"), whereas, smaller models have ranges of 0-150 mm (0"-6"), 0-200 mm (0"-8"), and so on.

Difference in Method of use 

Micrometers utilize a rotatable threaded spindle for fastening the workpiece, whereas calipers employ a linear moving sliding frame for the same purpose. 

Digital versions of these tools use a similar mechanism; however, they display the reading digitally.

Difference in Ease of use

Calipers are simpler to understand and easier to use than micrometers, which have a slower operation and require greater skill.

A manual micrometer consists of three scales: vernier, thimble (rotating), and sleeve scales.

When measuring the dimensions of a workpiece, the observer has to take exact readings of all three scales to determine the accurate dimension.

On the other hand, calipers consist of two scales: the main scale and the vernier scale, which are comparatively easier to read than the scales of micrometers.

However, this shortcoming is eliminated by using digital variants of these instruments, as they provide a digital readout of the exact measurement without the need for reading multiple scales.

Difference in Application/Uses

Calipers are versatile tools that can be used for measuring internal and external diameters of workpieces with different shapes.

Some calipers can also be used to measure the depth of the workpiece by using the depth blade at the back of the caliper.

Moreover, the sharp jaws of the caliper can also be used to mark the measured point by scratching the surface.

However, using them to mark tough surfaces can damage the caliper and affect its accuracy.

On the other hand, depending upon its jaw design, a micrometer can measure either the outer dimensions or the internal dimensions of an object.

Both these instruments are commonly used in mechanical workshops, research labs, and manufacturing plants for measuring the dimensions of different objects, e.g., the internal diameter of a hollow spur gear, the depth of a blind hole, etc.

Moreover, these tools can also be attached to different auxiliary equipment. 

For instance, some drill presses house calipers to measure the depth and diameter of a drilled hole. 

Difference in Components/Parts

A micrometer consists of an anvil (fixed surface) and spindle (moving surface) to aid in fastening an object, while a caliper houses two internal and two external jaws for the same purpose. 

The anvil is usually flat-shaped, but some models also house a ball-shaped or tubular-shaped anvil. 

On the other hand, the caliper's jaws are generally flat and pointed.

For tightening the grip, a micrometer houses a ratchet that rotates, whereas calipers contain a thumbscrew that rolls.

In micrometers, the thimble scale rotates when taking a measurement, while the remaining scales move linearly, whereas in calipers, all scales move linearly during the measurement.

Difference in Cost

Micrometers are slightly more expensive than calipers due to their higher accuracy.

Calipers usually cost between $10 to $20, with high-quality calipers ranging up to $75.

Micrometers usually cost between $30 to $50, but high-end models cost more than $100.

Difference in Categorization

Calipers and micrometers are categorized based on different factors.

Micrometers are classified into different types based on their anvil and spindle geometries, scale limits, and precision. The most common types are outside, inside, and depth micrometers.

Calipers are categorized based on jaw geometries, scale limits, and precision. Vernier calipers and digital calipers are the most popular types widely in use.

Which One to Choose for Your Application: Micrometer or Callipers?

There are several factors needed to determine which measuring tools suit your need.

Type of Material

Although both devices can be used for measuring any type of material, micrometers consist of a ratchet arrangement that prevents the movement of the jaws beyond the material thickness.

On the other hand, calipers do not contain a ratchet arrangement, and the jaws are tightened manually by moving the thumb wheel.

Over-tightening of the jaws against the workpiece can result in indenting on the surface of the workpiece, leading to inaccurate measurement.

Especially when measuring soft materials like foam, plastics, aluminum, etc.

Therefore, micrometers are a better choice for measuring soft workpieces without the risk of deforming or indenting their surface.

Shape of the Workpiece

A caliper is more suitable for comparatively larger workpieces like shafts and rods, whereas a micrometer is ideal for measuring small-sized workpieces like wires, pins, sheets, etc.

Apart from that, the jaws of the caliper provide the ability to measure internal, external, and depth dimensions of the workpiece by a single device.

Whereas a single micrometer can be used for measuring either the outer dimensions or internal dimensions of workpieces.

Familiarity With Instrumentation

Understanding and using calipers is much easier, especially for novice users. With minimal training, DIY users and hobbyists can use calipers conveniently.

After acquiring skills and expertise in handling calipers, you can familiarize yourself with a micrometer, which will require significant practice to master.

Speed to Accuracy Requirement

In bulk production industries, measurements must be performed quickly to optimize production efficiency.

For instance, in large-scale production of gears, a general idea of final dimensions is required as each stage in such processes is already carefully controlled to ensure superior quality products.

Calipers are ideal for such applications where quick measurement of workpieces is the priority.

In contrast, micrometers are best suitable for applications that require a tight tolerance and high accuracy, such as research activities in laboratories, prototyping, etc.

Type of Application

The type of application also governs the selection of the measuring tool. 

If an object with complex geometry requires the measurement of intricate dimensions, a micrometer would be better suited due to its higher accuracy and precision.

Applications involving the measurement of very thin and small objects require a micrometer to take an accurate reading of its dimensions.

For example, a micrometer would be preferred to measure the thickness of a printed circuit board (PCB), as these boards are generally thin and cannot be measured precisely by a caliper. 

Even slight inaccuracies in dimensions can cause serious defects in products. In this case, a thinner circuit board may not be able to sustain thermal stresses and fail under operation.

Digital vs Manual Devices

With technological advancements, the digital versions of these measuring instruments are increasingly becoming common.

They possess few advantages over their manual counterparts.

Parameter	Digital	Manual
Speed	Faster	Slower
Ease of Use	Easier	Tedious
Cost	Higher	Lower
Service Life	Shorter	Longer
Accuracy	Higher	Shorter

Digital calipers and micrometers are generally faster as they quickly provide the digital readout of the measurement on the LCD screen, eliminating manual calculations.

The digital versions are also easier to use, as they eliminate the need for multiple scales, which could be difficult to read for beginners.

Furthermore, the requirement to read multiple scales on manual versions makes the process very tedious and prone to mathematical errors.

Digital instruments usually cost comparatively more than manual versions, making them unfeasible for DIY users and hobbyists. However, for industrial and laboratory usage, they are better suited.

The digital instruments have a lower life as their LCD, controller, and wiring is vulnerable to damage from water or other contaminants.

Manual models, on the other hand, can be easily used in harsh environments without any damage.

Digital models prevent human or parallax errors, rendering their readings more accurate than manual readings.  

Overall, if cost and outdoor usage are the major factors when selecting the instrument, manual models are the way to go.

But, if factors such as speed and accuracy are the primary requirements, digital instruments lead the way. 

Final Thoughts

Calipers and micrometers both hold crucial importance as measuring tools.

While calipers are suitable for measuring comparatively larger workpieces, micrometers are ideal for measuring small workpieces with higher resolution.

Furthermore, calipers are comparatively cheaper, more versatile, and easy to use, making them ideal for beginners and DIY users.

Therefore, it is important to identify your requirements before selecting the right instrument for your application.

Frequently Asked Questions (FAQ)

What precautions should be taken while using calipers and micrometers?

While using calipers and micrometers, ensure that you do not pinch the jaw edges beyond their limits, and always ensure that your fingers are away from the jaws or the spindle when operating the device.

What is a zero error in a caliper or micrometer?

A zero error in a caliper or micrometer is when the instrument reads a value other than zero, even at the absolute zero position. This error commonly arises due to incorrect calibration.

What material are calipers and micrometers composed of?

Calipers and micrometers are usually composed of hardened steel.