Wholesale Jewelry-Making Supplies for Professional Craftspeople
1 (800) 366-2156

Not too sure about millimeters?

In case you've never gotten along with millimeters, or in case you need to do some conversions and never got along with algebra, this page contains easy conversions back and forth between inches and millimeters.

Sections on this page:

• Easy estimates, without a calculator
  • Inch-to-Millimeter
  • Millimeter-to-Inch
• How to make Exact Conversions, with a calculator
  • Inch-to-Millimeter
  • Millimeter-to-Inch
• Other miscellaneous conversion units

If you have the inches, and need to know the millimeters:

• 1/16 inch = almost 2mm
• 1/8 inch = just barely over 3mm
• 1/4 inch = just barely over 6mm
• 3/8 inch = almost 10mm
• 1/2 inch = almost 13mm
• 5/8 inch = 16mm
• 3/4 inch = 19mm
• 7/8 inch = just barely over 22mm
• 1 inch = 25.4mm

If you have the millimeters, and need to know the inches:

• 1mm = just over 1/32 inch
• 2mm = just over 1/16 inch
• 3mm = almost 1/8 inch
• 4mm = 5/32 inch (= a bit over 1/8 inch)
• 5mm = just over 3/16 inch
• 6mm = almost 1/4 inch
• 7mm = almost 9/32 inch (= a bit over 1/4 inch)
• 8mm = 5/16 inch
• 9mm = almost 3/8 inch
• 10mm = just over 3/8 inch
• 11mm = almost 7/16 inch
• 12mm = almost 15/32 inch (= almost 1/2 inch)
• 13mm = just over 1/2 inch
• 14mm = almost 9/16 inch
• 15mm = almost 19/32 inch
• 16mm = 5/8 inch
• 17mm = almost 11/16 inch
• 18mm = just over 11/16 inch
• 19mm = 3/4 inch
• 20mm = 25/32 inch
• 21mm = just over 13/16 inch
• 22mm = almost 7/8 inch
• 23mm = 29/32 inch
• 24mm = just over 15/16 inch
• 25mm = almost 1 inch

If you have inches, and want to know how many millimeters:

• Step one: Convert any inch fractions to decimals.
  Example: 1/4 inch = 1 divided by 4 = .25 inch
  Example: 1/16 inch = 1 divided by 16 = .0625 inch
  
  For amounts over an inch, you want to first convert the fractional part, then add the whole inches part:
  
  Example: 2-1/4 inch = 1 divided by 4, plus 2 = 2.25 inch
  Example: 1-5/8 inch = 5 divided by 8, plus 1 = 1.625 inch

• Step two: Now multiply that decimal by 25.4
  For each of the above examples, the complete steps would be:
  1/4 inch = 1 divided by 4, x 25.4 = 6.35mm (6mm)
  1/16 inch = 1 divided by 16, x 25.4 = 1.5875 (1.6mm)
  2-1/4 inch = 1 divided by 4, plus 2, x 25.4 = 57.15 (57mm)
  1-5/8 inch = 5 divided by 8, plus 1, x 25.4 = 41.275 (41mm)

If you have millimeters (or centimeters), and you want inches:

• Step one: Divide your millimeter amount by 25.4
  (or divide your centimeter amount by 2.54)
  Example 1: 2mm divided by 25.4 = .07874 inches
  Example 2: 6mm divided by 25.4 = .2362 inches
  Example 3: 30mm divided by 25.4 = 1.1811 inches
  Example 4: 4cm divided by 2.54 = 1.5748 inches
  

If, however, you want fractions of an inch (1/16, 1/4, 1/2), rather than a decimal, try this:

• Step two: Converting your decimal to a useable fraction:
  I prefer to round to the nearest 1/16 of an inch. To round to the nearest 1/16 of an inch, multiply your decimal by 16. The resulting number is how many 1/16's of an inch you have.
  Using the numbers from Step 1 above:
  .07874 times 16 = 1.26, which rounds to 1, so about 1/16 inch.
  .2362 times 16 = 3.779, or rounds to 4, so about 4/16. 4/16 = 1/4 inch
  
  For amounts over an inch, it is easiest to remove the whole inches, and add them back in after you convert the portion after the decimal point:
  1.1811 Removing the 1 gives you .1811 times 16 = 2.9, which rounds to 3, so about 3/16 inch... don't forget to add the 1 back on, so this is really 1-3/16 inch.
  1.5748 Removing the 1 gives you .5748 times 16 = 9.1968, which rounds to 9, so about 9/16 inch... don't forget to add the 1 back on, so this is really 1-9/16 inch.

• inches to millimeters, multiply by 25.4.
• inches to centimeters, multiply by 2.54
• millimeters to inches, divide by 25.4
• centimeters to inches, divide by 2.54

• meters to feet, multiply by 3.28
• feet to meters, divide by 3.28

• millimeters to centimeters, multiply by 10
• centimeters to meters, multiply by 100