How Many Inches is 21 cm?

When it comes to converting between metric and imperial units of measurement, there are a few key conversions that are useful to know. One of these conversions is between centimeters and inches.

In this article, we will walk through how to convert 21 cm to inches step by step.

How Many Inches is 21 cm?

Step 1: Understand the Conversion Factor

The conversion factor between centimeters and inches is 2.54. This means that there are 2.54 centimeters in one inch. This conversion factor can be used to convert from centimeters to inches and vice versa.

Step 2: Write out the Conversion Equation

To convert 21 cm to inches, we need to use the conversion equation:

21 cm * (1 inch / 2.54 cm)

Notice that we have written the conversion factor as a fraction, with inches on top and centimeters on the bottom. This is because we want the centimeters to cancel out, leaving us with inches as our final unit of measurement.

Step 3: Simplify the Equation

Now we can simplify the equation by multiplying 21 cm by 1 inch and dividing by 2.54 cm:

21 cm * (1 inch / 2.54 cm) = (21 * 1) / 2.54 inch = 8.2677 inch

We now have our answer in inches, but we should round it to a reasonable number of decimal places. In general, it is common to round to two decimal places for measurements like this.

Step 4: Round to Two Decimal Places

Rounding 8.2677 to two decimal places gives us:

8.27 inch

Therefore, 21 cm is equal to 8.27 inches when rounded to two decimal places.

Step 5: Check Your Answer

To check our answer, we can perform a quick mental check. Since we know that there are 2.54 centimeters in one inch, we can estimate that 21 cm is slightly less than 10 inches. Our answer of 8.27 inches makes sense, since it is less than 10 inches.


In summary, to convert 21 cm to inches, we used the conversion factor of 2.54 cm/inch to write out the conversion equation. We then simplified the equation and rounded our answer to two decimal places. The final answer is 8.27 inches.






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