Square Millimeters and Square Inches Converter

Using the Square Millimeters and Square Inches Converter

The converter above allows you to find equivalent values of the smallest commonly used unit of area within the metric system (the square millimeter) and the smallest commonly used unit of area within the imperial system (the square inch).

Start by choosing the preferred spelling for this converter. The choice is between the British and the American spelling, which will modify in what way the word ‘meter’ is spelled (which will change to ‘metre’ if you select the British spelling).

The next step is to choose your input and output values.

The input units are chosen in the ‘CONVERT FROM’ section, where you can choose from 2 options, the square millimeters ($mm^2$) and the square inches ($in^2$).

The output units can be selected in the ‘CONVERT TO’ section and the choice is between the same 2 units as for the input.

Alternatively, you can just stick to the default settings or swap the input and output units by clicking on the icon with 2 arrows headed in opposite directions.

Once your units are chosen, move toward the ‘VALUE TO CONVERT’ section, where you will type in the input value as a decimal number using the decimal dot (the reason we mention this is, that in some countries a comma is used to represent a decimal number).

Follow up by choosing the number of decimal places you want your result rounded toward and then click on ‘CONVERT’.

Your result will appear below the converter as a decimal number rounded to your desired number of decimal places, alongside a convenient ‘COPY’ icon which allows you to copy and paste your result elsewhere easily.

A conversion rate between the input and output values is also included in the result. The significance of this rate will be explained in the next section.

Converting Square Millimeters and Square Inches Manually

In order to convert manually between any 2 units, we must find the conversion rate between the units.

A conversion rate is essentially an expression that describes the value of a unit, which equals 1 measure of the other unit, and vice versa.

Hence, we must express the number of square millimeters that are equivalent to 1 square inch and also the number of square inches that are equal to 1 square millimeter.

Since both units are square units, we can start by showing the equivalent values of the units of length that define them (which are millimeters and inches).

1 inch is equivalent to approximately 25.4 millimeters.
1 millimeter is equivalent to approximately 0.039 inches.

In order to change these expressions into equivalent values for the units of area, we simply square every value and unit in said expression. That results in the following equivalent values.

1 square inch is equivalent to approximately 645.16 square millimeters.
1 square millimeter is equivalent to approximately 0.001521 square inches.

Hence the conversion rates are as follows.

The conversion rate between square inches and square millimeters is 1:645.16, or 100:64,516 which simplifies to 25:16,129.
The conversion rate between square millimeters and square inches is 1:0.001521, which simplifies to 1000,000:1521.

Keep in mind that these 2 conversion rates are rounded to a convenient number of decimal places, which will cause slight, but not very significant, inaccuracies when calculating manually. For a more accurate result, use our converter.

The conversion rates lead toward 2 formulae that will help us with converting between the units manually.

$MM^2$ = $IN^2$ x 645.16

$IN^2$ = $MM^2$ x 0.001521

EXAMPLE 1: What is the area in square millimeters of a 1.1 $in^2$ stamp?

The problem has an input in square inches while calling for an output in square millimeters. This makes the first formula suitable for solving this problem, as we only need to substitute 1.1 for $in^2$ and then solve using multiplication.

$MM^2$ = $IN^2$ x 645.16 = 1.1 x 645.16 = 709.676 $mm^2$

EXAMPLE 2: What is the area in square inches of a sheet of paper with an area of 17,543 $mm^2$?

This problem calls for the second formula, as the output is in square inches, which is also the subject of the second formula. We substitute 17,543 for $mm^2$ and count as follows.

$IN^2$ = $MM^2$ x 0.001521 = 17,543 x 0.001521 = 26.682903 $in^2$.

Evolution of Phone Screen Sizes

The phone screen size is part of the phone that has been on an almost steady increase since the conception of the commercially available mobile phone around the year 2000. The table below offers a quick glance at the average area of the screen of mobile phones throughout the last 2 decades. Notice that the table is not split into equally large intervals, but instead breaks up the last 2 decades into parts where there were significant size changes.