Inches to Centimeters Converter

Shipping labels, customs declarations and international marketplace listings often ask for dimensions in centimeters, while your tape measure or the product box gives inches. Convert each dimension separately and keep them in the same order the form asks for.

A parcel measuring 16 × 12 × 8 in becomes:

If the form only takes whole numbers, entering 41 × 31 × 21 cm is the safer choice for a box. Rounding 40.64 down to 40 declares a parcel smaller than the one you are actually sending.

You can type a tape-measure reading as it is written. Put a space between the whole inches and the fraction, as in 11 1/4, and the converter reads it as 11.25 in. A fraction on its own, such as 3/16, works too. What it can't read is the inch mark: 11 1/4" gets a note that the number couldn't be read, so leave the quote off.

The common fractions, with their decimal forms for checking a result:

So a picture frame measured at 11 1/4 in comes out at 28.575 cm, whether you type the fraction or 11.25.

The factor 2.54 splits neatly into 2.5 and 0.04. Multiply by 2.5 (ten times the number, divided by four), then add 4% of the original number. The result is exact, not an estimate.

• 12 in: 12 × 2.5 = 30, and 4% of 12 is 0.48, giving 30.48 cm.
• 18 in: 45 + 0.72 = 45.72 cm.
• 24 in: 60 + 0.96 = 60.96 cm.

If you skip the second step and stop at × 2.5, your answer is 1.6% too low. On a single inch that is invisible, but on a 24-inch side it drops almost a full centimeter.