When you start making jewelry for fun or as a business, you’ll probably wish (not for the first time) that you were taught the metric system instead of the imperial as a kid.
Sure, most of us learned it temporarily for science class in high school, but all that has made it’s way far out of our brains.
Which means you’re probably googling millimeters to inches conversions every time you go to buy beading supplies online.
And while we can’t make you learn the conversions for good, we can help you out by putting everything you need in one place. Read below to get the conversion chart you’ve been missing – and some millimeter to inches tips and tricks!
Metric System Reminder
If you’re just looking for the plain conversions, go ahead and skip this section. But if you’re one of those people that needs to know why something is the way it is, here you go.
The metric system makes a lot more sense than imperial. Why? It’s all based on units of ten.
The middle form of measurement is a meter or a gram (for our purposes). A Deci-meter is 10x smaller than a meter, a centimeter is 100 times smaller than a meter, and a millimeter is 1000 times smaller than a meter.
Basic Conversions
- 1 Meter = 39.3 inches
- 1 Yard = .91 meter
- 1 Foot = .30 (30%) meter
- 1 Inch = 2.54 centimeter
- 1 Inch = 25.4 millimeter
- 1 Millimeter = .04 inch (4% inch)
The Millimeters to Inches and Inches to Millimeter Formula
If you’re old-school and you like to put things on pen and paper (and don’t want to print this article out), here’s the formula for converting inches to millimeters, and mm to inches. Since 1 inch is equal to 25.4 millimeters, you want to write that down.
The formula you need to convert the two is:
D(mm) = D(inches) x 25.4
In plain English, that’s the number of millimeters equal to the number of inches, multiplied by 25.4.
Let’s go through an example. Let’s say you have a bead that’s 10 millimeters, and you want to know how big that is in inches.
You would set up the problem as: 10 = x * 25.4
Then you’d pull out those old algebra skills and divide the right side by 25.4, then the right side (10/25.4).
Once you did the math, you’d get the answer 0.394, which tells you that 10 millimeters are about 40% an inch – or about 1 centimeter.
Millimeters to Centimeters
Since you probably know what a centimeter is off the top of your head better than a millimeter, let’s go over that conversion.
Don’t worry if you’re not a math person – there’s a chart you can copy down or print out of all these conversions at the end. We’ve even added in a chart that shows you how many beads you need for certain necklace lengths (which are in inches, thankfully).
Want to know about ring sizes conversions from standard size into millimeters? We have that too. It’s all below!
MM to CM Formula
Since the metric system is a lot easier than the imperial, this formula is easier than the last. To find out the number of centimeters in a millimeter, take the number of millimeters and divide by 10.
That’s it! The official formula is: CM=mm/10
To put it another way, there are 10 mm in one centimeter. Yes – a mm is that small!
Working Jewelry Conversion Charts
Okay – if you just scrolled down here to get to the easy part, that’s okay.
We’ll start with general conversions, move to bead size, then do necklace lengths.
General MM to Inch Conversion Chart
- 1 mm = .03937 in (1/25th)
- 2 mm = .07874 in (1/16th)
- 3 mm = .0.11811 in (3/32)
- 4 mm = 0.15748 in (1/8th)
- 5 mm = 0.19685 in (3/16th)
- 6 mm = 0.23622 (approx 1/4)
- 7 mm = 0.27559 (1/4 +1/16)
- 8 mm = 0.31496 (5/16th
- 9 mm = 0.35433 (approx 3/8)
- 10mm = 0.39370 (3/8 & 1/16)
- 10 mm = 1 centimeter
- 11 mm = 0.43307 in (7/16th)
- 12 mm = 0.47244 in (approx 1/2)
- 13 mm = 0.51181 in (1/2 & 1/16)
- 14 mm = 0.55118 in (9/160
- 15 mm = 0.59055 in (approx 5/8)
- 16 mm = 0.62992 in (5/8)
- 17 mm = 0.66929 in (11/16)
- 18 mm = 0.70866 in (approx 3/4th)
- 19 mm = 0.74803 in (3/4)
- 20 mm = 0.78740 in (approx 13/16)
- 21 mm = 0.82677 in (13/16 +)
- 22 mm = 0.86614 in (approx 7/8)
- 23 mm = 0.90551 in (7/8+)
- 24 mm = 0.94488 in (15/16)
- 25 mm = 0.98425 in (1 inch)
Beads Per Strand
While it’s nice to know exactly the size of the bead, here’s a good idea of how many different size beads you need per strand (on average).
There are four common lengths of necklaces, 16 inches, which s a little longer than a choker, a 20-inch strand that reaches mid-decolletage, a 24-inch strand that lands in the middle of the chest, and a 36-inch strand that reaches to about the bottom of the breasts.
Please note that different body sizes determine where each necklace length sits on different people. It’s common to offer necklace extenders on your website so that everyone can wear the size of their choosing.
16 Inch Strand
- 136 – 3mm
- 67 – 6mm
- 40 – 10mm
20 Inch Strand
- 169 – 3mm
- 85 – 6mm
- 42 – 10m m
24 Inch Strand
- 203 – 3mm
- 102 – 6mm
- 61 – 10mm
36 Inch Strand
- 305 – 3mm
- 152 – 6mm
- 92 – 10mm
Ring Size Conversions
It’s relatively uncommon to use our beads to make rings, but if that’s your art form, we support it.
MM to Ring Size
- 5 = 15.6mm
- 6 =16.6 mm
- 7 = 17.2 mm
- 8 = 18.1mm
- 9 = 19.1mm
- 10 = 19.7 mm
Millimeters to Inches Made Simple
As a budding jewelry artist, we hope that our millimeters to inches and more guide made things simpler for you.
Feel free to print this page for your workstation, and browse our site for your bead-related needs!
We have jewelry making kits, wholesale beads, Murano glass beads, and more! You can find everything you need to make your own jewelry (including completed pieces) to everything you need to start an Etsy shop on our site.
Wondering how to make great jewelry? Read our blog for more information! It’s filled with more helpful articles like this that will take you from beginner to expert in no time.