Here is how to convert 21 mm to inches. We will give you the fractional answer, the decimal answer, and illustrate the answer on our tape measure.
One millimeter is equal to 5/127 inches, and 21 as a fraction is 21/1. Therefore, to get the fractional answer to 21 mm in inches, we multiply 21/1 by 5/127 and simplify if necessary.
cm × 5/127 = inches
21/1 × 5/127 = inches
21/1 × 5/127 = 105/127
21/1 mm = 105/127 inches
21 mm = 105/127 inches
As promised above, we also have the answer to 21 mm in inches in decimal form. Although the fractional answer above is exact, the decimal answer may be rounded if necessary:
105/127 ≈ 0.826771653543307
105/127 ≈ 0.82677
21 mm ≈ 0.82677 inches
Our image below shows 21 mm on a tape measure. The top row of the tape measure is inches, and each mark on the bottom row is 1 millimeter (10 millimeter marks equal 1 centimeter).
As you can see, we drew a red line where 21 mm and 0.82677 inches meet on the measuring tape.
Millimeters to Inches Calculator
Here you can convert another length in millimeters to inches.
What is 21.1 mm in inches?
Here is another inches to millimeters calculation that we have done for you.