30 mm = 1.1811 inches, usually rounded to 1.18 inches.
It is also exactly 3 centimeters. That makes 30 mm a little longer than 1 inch. The examples below can help you picture the size more easily.
How Big Is 30 mm?
Thirty millimeters is a small measurement.
Since 1 inch equals exactly 25.4 mm, a length of 30 mm is 4.6 mm longer than 1 inch.
On a metric ruler, 30 mm is easy to find. It is exactly the distance from 0 to the 3 cm mark.
In fractional inches, 30 mm is close to 1 3/16 inches. That is only an approximation, because 1 3/16 inches actually equals 30.1625 mm.
30 mm in Other Units
Here are the most useful conversions for 30 mm.
| Unit | 30 mm equals |
|---|---|
| Inches | 1.1811 in |
| Centimeters | 3 cm |
| Meters | 0.03 m |
| Feet | about 0.0984 ft |
| Fractional inches | about 1 3/16 in |
The centimeter value is exact. The inch and foot values above are rounded for easier reading.
Everyday Things Close to 30 mm
No everyday object should be treated as exactly 30 mm unless its size is actually specified that way. Some of the examples below are slightly smaller or larger.
1. U.S. Half Dollar
A U.S. half-dollar coin has an official diameter of 30.61 mm.
That makes it one of the closest familiar comparisons to 30 mm. The coin is only 0.61 mm wider.
If you have seen a half dollar, its width gives you a very good idea of what 30 mm looks like.
2. Large 48L Button
A 48 ligne, or 48L, button is commonly listed at about 30 mm in diameter.
Buttons of this size may be used on coats and other larger clothing items. Button sizes can vary by manufacturer, so this is best treated as a common industry size rather than a rule for every button.
3. Three AAA Batteries Side by Side
A standard AAA battery is roughly 9.5 to 10.5 mm in diameter.
Three placed side by side would measure about 28.5 to 31.5 mm across.
That puts three AAA batteries very close to 30 mm, although the exact total depends on the batteries.
4. Two AA Batteries Side by Side
An AA battery is roughly 13.5 to 14.5 mm wide.
Two placed next to each other would measure about 27 to 29 mm across.
That means two AA batteries are usually a little narrower than 30 mm, but still close enough to be useful for comparison.
5. U.S. Quarter
A U.S. quarter has an official diameter of 24.26 mm.
So 30 mm is 5.74 mm wider than a quarter.
If you picture a quarter and add a few millimeters around its edge, you get close to a 30 mm circle.
6. Typical Wine Cork
Many natural wine corks are around 24 mm in diameter.
That makes a typical cork about 6 mm narrower than 30 mm.
Cork sizes vary depending on the bottle and type, so this is only an approximate comparison.
7. Four-Stud LEGO Brick
A standard four-stud LEGO brick is roughly 31.8 mm long.
That makes it about 1.8 mm longer than 30 mm.
So 30 mm is just a little shorter than the length of a typical four-stud LEGO brick.
8. Standard Poker Chip
A standard casino-style poker chip is commonly around 39 mm in diameter.
That makes it about 9 mm wider than 30 mm.
A 30 mm circle would therefore look noticeably smaller than a normal poker chip.
9. 30 mm Screw or Bolt
Metric screws and bolts are often sold with a 30 mm nominal length.
For example, a product marked M4 × 30 mm uses 30 mm as its stated length.
The way the length is measured depends on the type of screw head, so the full end-to-end length is not always exactly 30 mm.
10. 30 mm Watch Case or Hoop Earring
Some watches are sold with a 30 mm case size, and some hoop earrings are sold as 30 mm hoops.
These can give you a direct visual example of the measurement.
The exact way 30 mm is measured depends on the product, so always check whether the listed size refers to width, diameter, or another dimension.
How to Convert 30 mm to Inches
The conversion is simple because:
1 inch = exactly 25.4 mm
To convert millimeters to inches, divide the millimeter value by 25.4.
For 30 mm:
30 ÷ 25.4 = 1.181102… inches
So:
30 mm = 1.1811 inches
For everyday use, you can round this to 1.18 inches.
25–35 mm to Inches Conversion Table
This table shows measurements close to 30 mm.
| Millimeters | Inches |
|---|---|
| 25 mm | 0.9843 in |
| 26 mm | 1.0236 in |
| 27 mm | 1.0630 in |
| 28 mm | 1.1024 in |
| 29 mm | 1.1417 in |
| 30 mm | 1.1811 in |
| 31 mm | 1.2205 in |
| 32 mm | 1.2598 in |
| 33 mm | 1.2992 in |
| 34 mm | 1.3386 in |
| 35 mm | 1.3780 in |
This also shows that 30 mm sits just above the 1-inch point, since 1 inch equals 25.4 mm.
Final Thoughts
30 mm equals 1.1811 inches, or about 1.18 inches. It is also exactly 3 cm.
For a simple real-life comparison, think of a U.S. half dollar. Its 30.61 mm diameter is very close to 30 mm.
Common Questions About 30 mm
Is 30 mm bigger than 1 inch?
Yes. 30 mm is 4.6 mm longer than 1 inch, because 1 inch equals 25.4 mm.
Is 30 mm the same as 1.2 inches?
Not exactly. 30 mm equals about 1.1811 inches, while 1.2 inches equals 30.48 mm.
They are close, but not the same.
Is 30 mm exactly 3 cm?
Yes. 30 mm equals exactly 3 cm because 10 mm equals 1 cm.
What fraction of an inch is 30 mm?
Thirty millimeters is approximately 1 3/16 inches.
This is only a close fraction. The more accurate decimal value is 1.1811 inches.
Where is 30 mm on a ruler?
On a metric ruler, 30 mm is exactly at the 3 cm mark.
On an inch ruler, it falls slightly below 1 3/16 inches.
Is a U.S. half dollar about 30 mm wide?
Yes. A U.S. half dollar is 30.61 mm in diameter, so it is only 0.61 mm larger than 30 mm.
Is a quarter 30 mm in diameter?
No. A U.S. quarter is 24.26 mm in diameter.
That makes it about 5.74 mm smaller than 30 mm.
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