Metrology - simulator

Conversion from millimeter to fractional inch and milesimal inch - transformation between units

If you need to convert a unit between fractional, milesimal inch and millimeter go to the page: Calculate linear dimensions in millimeter, fractional and milesimal inch and solve your problem, later come back here to learn how to do it.


roll down the page and interact
with the conversor of measures
Convert millimeter - gractional inch or milesimal inch - interactive conversor

This Interactive conversor of millimeter to inch Interativo de millimeter para polegada (and vice-versa) was created to facilitate your comprehension, to allow you to evaluate your results and antecipate them. It's utilization is very simple, roll down the page until the conversor, drag and drop the red line in the horizontally, by aligning the values ​​on the scales (millimeter 'mm' and inch 'in'). Just below them, the values ​​appear in millimeters, fractional inch (fractioned) and corresponding milesimal inch and the formula of calculation. After interacting, rol down the page to understand the mechanics of the calculation.

Before going on on this page, I recommend you to interact with the Fraction topic on page: Using the fractional inch understanding and measuring , later come back here, it's worthing!

Transformation of millimeter to inch it has no mistery


Inch ( polegada / polegadas in portuguese). Your abreviation is in , sometimes we see " (double quotes) or pol . It is a linear measure unit of English System, Imperial System, among others. Was based on the dimensions of the human body and the fractional number system (fractionated).

Some people maintain that its controversial origin is associated with the extent of the human thumb, another argues that its origin comes from the Latin word uncia that means "one twelfth" so, inch is an uncia , or 1/12, the foot.

Later, beyond the fractional system, it became to be divided by the decimal system, this way we have two division systems of inches that we have to know about: the fraction (eg.: 1/128") and milesimal (eg.: 0.025in). The milesimal system is also known as milesimal of inch (mil) the notation of the previous example is 25mil (twenty-five thousandths of an inch).

Nowadays, and by definition, the yard was standardized as 0.9144m. A yard is aproximatelly to 3 foot -table 1, a inch, that is 1/12 of a foot, and it's aproximatelly to 2.54cm or 25.4mm (unit used in the metrology, mechanical engeneering and in the metal mechanic ofices). 0.9144/(3*12)

Thus, 1in = 25.4 mm. So we have 25.4 mm/in (25.4 millimeters by "for each" inch)-Figure 1 (note that in Interactive conversor (simulador) there are two parallel horizontal lines of the same length. They are equivalent to 1.000in and 25.4mm - 1 ") (bounded by 0 and 1).

mm equivalent inch => 25.4mm/in

figure 1

Conversion of inch to millimeter

Transformation of inch to millimeter? Nothing more easy!

Fractional inch to milesimal inch

The fractional inch is the one represented as a fraction, for example: 1/2" (half inch); 1/4" (a quarter of inch); 7/16"(seven sixteenths inch); 3.5/128" (three inches five hundred twenty eight cents).

To convert to milesimal inch form simply divide the fraction and add the integer part. See:

  • 1/2" -> one divided by two -> 0.5"
    • observe that in the english system the point used as separator of the integer part (zero) of the decimal part (five) of number
  • 1/4" -> one divided by four -> 0.25"
  • 7/16" -> seven divided by sixteen -> 0.4375"
  • 3.5/128" five divided by one hundred and twenty eight and added three -> 3.0391"

Milesimal inch to millimeter

Just multiply the measure in milesimal inch by 25.4mm/in. See:

  • 0.5in * 25.4mm/in = 12.7mm
  • 0.25in * 25.4mm/in = 6.35mm
  • 0.4375in * 25.4mm/in = 11.112mm
  • 3.0391in * 25.4mm/in = 77.192mm

Fractional inch to millimeter

Just transform the fractional inch in milesimal inch and multiplicate the meausre in milesimal inch by 25.4mm/in. See this example: 1.3/8" (or 1.3/8in or also a three-eighths inch). We will divide three by eight, to transform the fraction in mils of inch, will add the integer part and multiply by 25.4 mm/in.

  • 3/8 = 0.375in
    • three hundred seventy-five mil
    • observe that in the english system the point is used as separator of the integer decimal part of the number
  • 0.375in + 1in = 1.375in
  • 1.375in x 25.4mm/in =34.92mm

other example: we will transform 5.1/8in (five and one-eighth inch) in millimeter: we will divide one by eight (1/8 = 0.125), and add five and multiplicate by 25.4mm/in-figure 2.

inch to millimeter conversion of

figure 2

Conversion of millimeter to fractional inch or milesimal

It's a little bit more difficult, but it's also easy, just divide the measure in millimeter by 25.4 mm/in. See this example: 70 mm. We will divide 70mm by 25.4mm/in obtainning 2.756in (or two thousand seven hundred fifty-six mils) already is the milesimal inch.

To convert to fractional inch, subtract the integer part and keep it: 2.756in - 2in=0.756in. Multiply this value by 128/128 (that is the lower fraction of inch used in the mechanical engineering, besides being equivalent to one -that os the neutral element of multiplication) and obtain as result 96.77/128. Round the numerator 97/128in and add the whole number that was reserved: 2.97/128in. With no intention to make anymore decorate, the fact that the numerator is an odd number indicates that it is necessary to simplify the fraction. If the numerator is even simplify the fraction - Figure 3.

  • 70mm / 25,4mm/in = 2.756in (milesimal form of inch)
  • 2.756in - 2in = 0.756in
  • 0.756in x 128/128 = 97/128in
  • 2in + 97/128in = 2.97/128in


  • 88.9mm / 25.4mm/in = 3.500in
  • 3.500in - 3in = 0.500in
  • 0.500in x 128/128 = 64/128 (64 is an even number)
  • 64/128 = 32/64 = 16/32 = 8/16 = 4/8 = 2/4 = 1/2
  • 3in + 1/2in = 3.1/2in
transformation of a millimeter to inch

figure 3

Equivalence between units of linear systems Metric and English

table 1

Millimeter - a thousandth of a meter

Meter , from greek metron = measure. Your abreviation is m (minuscule). That is a unit of linear measure of International System. Was based on the size of the earth and the decimal number system. His thousandth part is millimeter abreviation mm (minuscules), widely used in mechanical engineering.

Names and symbols to prefixes of Meter

Virtual Interactive Conversor:
conversion of linear measures between millimeter, fractional inch and milesimal

How to use the interactive conversor millimeter to fractional inch or milesimal

The utilization is very simple, drag and drop the vertical line in the horizontal, aligning the values in the scales (millimeter 'mm' and inch 'in'). Just below them, t will appear the corresponding values in millimeters, fractional inch and milesimal inch and the formula to the calculation.

This Interactive Conversor of millimeter to inch (and vice-versa) was designed to facilitate comprehension, allow you to evaluate your results and anticipate.

To better comprehension, take a look in the pages:

Use of meausres in fractional inch - understanding and applying
Use of paquimeter in fractional inch - measuring and interpreting
Table of conversion between fractional inch, milesimal inch, foot and millimeter
Calculate linear dimensions in millimeter, fractional inch and milesimal inch
Conversion program between linear units: transformation between Millimeter, fractional Inch and Milesimal

Eduardo J. Stefanelli -