Convert Inches to Millimeters

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

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1 in = 25.4 mm

How to Convert Inches to Millimeters

Tape measures can be used to measure units of length, and a calculator can be used to convert to another unit

Convert inches to millimeters with this simple formula:

millimeters = inches × 25.4

Converting an inch length measurement to a millimeter measurement involves multiplying the length by the conversion ratio to find the result. One inch is equal to 25.4 millimeters, so to convert simply multiply by 25.4.

For example, here's how to convert 5 inches to millimeters using the formula above.
5" = (5 × 25.4) = 127 mm

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

Inches and millimeters are both units used to measure length. Learn more about length and find more length measurement conversion calculators. Inches are an imperial measurement and can be abbreviated as in, for example 1 in. Millimeters are a metric measurement and can be abbreviated as mm, for example 1 mm. Learn more about the metric system, including the common unit prefixes and how to convert between metric units.

Millimeter is spelled millimetre internationally, and it is equal in length to .1 centimeters, 1000 micrometers, or 5/127 inch. They are represented by the smallest ticks on most metric rulers. To get a reference point of the size, the thickness of a dime is 1.35mm.

To get an idea of how small a millimeter is, a dime is 1.35mm thick.

The actual length of an inch has varied because of variances of the length of a foot. Throughout history it has been equal to 1/12 - 1/16 of a foot, but there are now exactly 12 inches in a foot. In 1959 the world agreed to the exact length of the national yard, .9144 meters. As such a foot is equal to .3048 meters and an inch is equal to 2.54 centimeters.

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

The standard ruler has 12", and metric combinations have 30 cm. Inches 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.

inches and millimeters are units used to measure length
Convert Millimeters to Inches

Inch Measurements and Equivalent Millimeter Conversions

Common inch values converted to the equivalent millimeter value
Inches Millimeters
1" 25.4 mm
2" 50.8 mm
3" 76.2 mm
4" 101.6 mm
5" 127 mm
6" 152.4 mm
7" 177.8 mm
8" 203.2 mm
9" 228.6 mm
10" 254 mm
11" 279.4 mm
12" 304.8 mm
13" 330.2 mm
14" 355.6 mm
15" 381 mm
16" 406.4 mm
17" 431.8 mm
18" 457.2 mm
19" 482.6 mm
20" 508 mm
21" 533.4 mm
22" 558.8 mm
23" 584.2 mm
24" 609.6 mm
25" 635 mm
26" 660.4 mm
27" 685.8 mm
28" 711.2 mm
29" 736.6 mm
30" 762 mm
31" 787.4 mm
32" 812.8 mm
33" 838.2 mm
34" 863.6 mm
35" 889 mm
36" 914.4 mm
37" 939.8 mm
38" 965.2 mm
39" 990.6 mm
40" 1,016 mm

More Inch Length Conversions

US Customary & Imperial Units
Convert to Miles
1" is equal to 1.5783E-5 miles
Convert to Yards
1" is equal to 0.027778 yards
Convert to Feet
1" is equal to 0.083333 feet
SI Units
Convert to Kilometers
1" is equal to 2.54E-5 kilometers
Convert to Meters
1" is equal to 0.0254 meters
Convert to Centimeters
1" is equal to 2.54 centimeters
Convert to Micrometers
1" is equal to 25,400 micrometers
Convert to Nanometers
1" is equal to 25,400,000 nanometers

Unit of Measurement Conversion Made Easy!

There are thousands of units of measure in use across the globe, and converting from one to another can be very difficult since each conversion requires a different formula to derive the result. Our unit of measurement conversion tools are meant to be dead easy. We break the mold of the typical dry and complicated experience. In addition to converting from one measurement to another, we provide the formula so you can see how the conversion is done, use it on you’re own calculator if you need to!

Convert units of length, weight, volume, and area between imperial and metric measures

Understanding the Metric System

The metric system makes it relatively easy to convert from one metric unit to another metric unit. The metric system uses a base unit, think meters or grams, and a prefix such as kilo or milli. The prefixes differ from the base units by differing powers of 10. So to convert within the metric system it’s usually a matter of multiplying or dividing by one of the powers of 10.

Here is a list of some of the common metric prefixes:

  • “kilo” – 1,000x larger
  • “hecto” – 100x larger
  • “deca” – 10x larger
  • “deci” – 10x smaller
  • “centi” – 100x smaller
  • “milli” – 1,000x smaller

There is a helpful mnemonic for remembering the prefixes: “King Henry Died Until Drinking Chocolate Milk.”
The u in Until refers to the base unit.