Millimeters to Inches Conversion Calculator

Enter the length in millimeters below to get the value converted to inches.

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1 mm = 0.03937 in
1 mm ≈ 3/64"
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How to Convert Millimeters to Inches

conversion scale showing millimeters and equivalent inches length values

The fastest and easiest way to convert mm (millimeters) to inches is use this simple formula:

inches = millimeters ÷ 25.4

Since there are 25.4 millimeters in one inch[1], the length in inches is equal to millimeters divided by 25.4. Thus, the formula to convert millimeters to inches is the length divided by 25.4.

For example, here's how to convert 5 millimeters to inches using the formula above.
5 mm = (5 ÷ 25.4) = 1.968504"
infographic showing how to convert millimeters to inches

Our inch fraction calculator can add millimeters and inches together and it also automatically converts the results to US customary, imperial and SI metric values.

Millimeters and inches are both units used to measure length. Keep reading to learn more about each unit of measure.

What is a Millimeter?

One millimeter is equal to one-thousandth (1/1,000) of a meter, which is defined as the distance light travels in a vacuum in a 1/299,792,458 second time interval.

The millimeter, or millimetre, is a multiple of the meter, which is the SI base unit for length. In the metric system, "milli" is the prefix for 10-3. Millimeters can be abbreviated as mm, for example 1 millimeter can be written as 1 mm.

Millimeters are often represented by the smallest ticks on most metric rulers. To get a reference point of the size, the thickness of a US dime is 1.35mm.[2]

What is an Inch?

An inch is a unit of linear length measure equal to 1/12 of a foot or 1/36 of a yard. Because the international yard is legally defined to be equal to exactly 0.9144 meters, one inch is equal to 2.54 centimeters.[3]

The inch is a US customary and imperial unit of length. Inches can be abbreviated as in, for example 1 inch can be written as 1 in.

Inches can also be denoted using the symbol, otherwise know as a double-prime. Often a double-quote (") is used instead of a double-prime for convenience. Using the double-prime, 1 in can be written as 1″.

A quarter is .955" in diameter, which is just smaller than 1"

The standard ruler has 12", and are a common measuring tool for measuring inches. They are also often measured using tape measures which commonly come in lengths from 6' - 35'. Other types of measuring devices include scales, calipers, measuring wheels, micrometers, yardsticks, and even lasers.

We recommend using a ruler or tape measure for measuring length, which can be found at a local retailer or home center. Rulers are available in imperial, metric, or combination with both values, so make sure you get the correct type for your needs.

If you need a ruler you can also download and print our free printable rulers, which include both imperial and metric measurements.

Millimeter Measurements and Equivalent Inch Conversions

Common millimeter values converted to the equivalent inch decimal and fraction values
Millimeters Inches (decimal) Inches (fraction)
1 mm 0.03937" 3/64"
2 mm 0.07874" 5/64"
3 mm 0.11811" 1/8"
4 mm 0.15748" 5/32"
5 mm 0.19685" 13/64"
6 mm 0.23622" 15/64"
7 mm 0.275591" 9/32"
8 mm 0.314961" 5/16"
9 mm 0.354331" 23/64"
10 mm 0.393701" 25/64"
11 mm 0.433071" 7/16"
12 mm 0.472441" 15/32"
13 mm 0.511811" 33/64"
14 mm 0.551181" 35/64"
15 mm 0.590551" 19/32"
16 mm 0.629921" 5/8"
17 mm 0.669291" 43/64"
18 mm 0.708661" 45/64"
19 mm 0.748031" 3/4"
20 mm 0.787402" 25/32"
21 mm 0.826772" 53/64"
22 mm 0.866142" 55/64"
23 mm 0.905512" 29/32"
24 mm 0.944882" 15/16"
25 mm 0.984252" 63/64"
26 mm 1.0236" 1 1/32"
27 mm 1.063" 1 1/16"
28 mm 1.1024" 1 7/64"
29 mm 1.1417" 1 9/64"
30 mm 1.1811" 1 3/16"
31 mm 1.2205" 1 7/32"
32 mm 1.2598" 1 17/64"
33 mm 1.2992" 1 19/64"
34 mm 1.3386" 1 11/32"
35 mm 1.378" 1 3/8"
36 mm 1.4173" 1 27/64"
37 mm 1.4567" 1 29/64"
38 mm 1.4961" 1 1/2"
39 mm 1.5354" 1 17/32"
40 mm 1.5748" 1 37/64"

References

  1. National Institute of Standards and Technology, SI Units - Length, https://www.nist.gov/pml/weights-and-measures/si-units-length
  2. United States Mint, Coin Specifications, https://www.usmint.gov/learn/coin-and-medal-programs/coin-specifications
  3. National Institute of Standards and Technology, Handbook 133 - 2019 Edition, https://www.nist.gov/sites/default/files/documents/2017/04/28/12-apde-gentab-11-hb133-final.pdf

More Millimeter Length Conversions

US Customary & Imperial Units
Convert to Miles
1 mm is equal to 6.2137E-7 miles
Convert to Yards
1 mm is equal to 0.001094 yards
Convert to Feet
1 mm is equal to 0.003281 feet
SI Units
Convert to Kilometers
1 mm is equal to 1.0E-6 kilometers
Convert to Meters
1 mm is equal to 0.001 meters
Convert to Centimeters
1 mm is equal to 0.1 centimeters
Convert to Micrometers
1 mm is equal to 1,000 micrometers
Convert to Nanometers
1 mm is equal to 1,000,000 nanometers