Inches to Millimeters Converter

Multiply inches by 25.4 to get millimeters — useful for tools, hardware and 3D printing.

1 in = 25.4 mm

Convert millimeters to inches instead

Formula

1 in = 25.4 mm

millimeters = inches × 25.4

Worked example

Convert 0.375 inches to millimeters

  1. Multiply by 25.4
  2. 0.375 × 25.4 = 9.525

0.375 in = 9.525 mm

Good to know

Fractional sizes convert as follows: 1/16 in = 1.5875 mm, 1/8 in = 3.175 mm, 3/16 in = 4.7625 mm, 1/4 in = 6.35 mm, 3/8 in = 9.525 mm, 1/2 in = 12.7 mm and 3/4 in = 19.05 mm. For drill bits, pick the nearest metric size and check the tolerance your job needs.

Conversion table

Inches to millimeters conversion table
Inches (in)Millimeters (mm)
0.06251.5875
0.1253.175
0.256.35
0.3759.525
0.512.7
0.62515.875
0.7519.05
125.4
1.538.1
250.8
376.2
4101.6
6152.4
12304.8

About these units

Inch (in)
Exactly 2.54 cm since the 1959 international yard and pound agreement. There are 12 inches in a foot.
Millimeter (mm)
One thousandth of a meter. Common on rulers, engineering drawings, screws and rainfall figures.