3/16 inch equals exactly 4.7625 millimetres, which is usually rounded to 4.76 mm.
That makes 3/16 inch slightly smaller than 5 mm. It is a small measurement often seen in drill bits, rivets, hex keys, dowels, rope, cable, and other tools or materials.
This article explains the exact conversion, how big 3/16 inch is, and some useful real-life comparisons.
How Many Millimetres Is 3/16 Inch?
3/16 inch = 4.7625 mm exactly.
First, convert the fraction to a decimal:
3 ÷ 16 = 0.1875 inch
Since 1 inch equals exactly 25.4 mm:
0.1875 × 25.4 = 4.7625 mm
Here are the most useful ways to write the measurement:
| Measurement | Value |
|---|---|
| 3/16 inch | 4.7625 mm |
| Rounded to 2 decimal places | 4.76 mm |
| Rounded to 1 decimal place | 4.8 mm |
| Centimetres | 0.47625 cm |
| Decimal inches | 0.1875 in |
For normal everyday use, 4.76 mm is usually accurate enough. For precise work, use the exact value of 4.7625 mm.
How Big Is 3/16 Inch?
3/16 inch is a little less than 5 mm.
The exact difference is:
5 mm − 4.7625 mm = 0.2375 mm
That is a very small difference, so 5 mm can help you picture the size. However, 5 mm and 3/16 inch are not exactly the same.
In centimetres, 3/16 inch is only 0.47625 cm, so it is less than half a centimetre.
This size is common in small hardware, tools, craft materials, tubing, and cables.
10 Things That Are About 3/16 Inch
Some of the best comparisons are objects that are actually sold in a 3/16-inch size. Others are only close to the measurement and are marked as approximate.
1. 3/16-Inch Drill Bit
A 3/16-inch drill bit has a nominal diameter of 3/16 inch, or 4.7625 mm.
This is one of the easiest ways to picture the measurement if you have a drill-bit set at home or in a toolbox.
The actual manufactured size may have tiny tolerances, but 3/16 inch is the stated bit diameter.
2. 3/16-Inch Wooden Dowel
Wooden dowels are available in a 3/16-inch diameter.
That means the dowel is nominally 4.7625 mm across.
A thin craft dowel in this size gives a clear visual idea of how wide 3/16 inch looks.
3. 3/16-Inch Steel Bearing Ball
Some small steel bearing balls are made with a diameter of 3/16 inch.
That equals 4.7625 mm.
A bearing ball this size is less than 5 mm wide, so it is quite small and easy to hold between two fingers.
4. 3/16-Inch Hex Key
3/16 inch is also a standard imperial hex-key or Allen-key size.
The width across the flats of a 3/16-inch hex key is nominally 4.7625 mm.
It is close to a 5 mm hex key, but the two sizes are not identical.
5. 3/16-Inch Pop Rivet
Pop rivets are commonly sold with a 3/16-inch body diameter.
That makes the body roughly 4.76 mm wide.
Rivets in this size are often used for joining thin pieces of metal or other materials.
6. 3/16-Inch Braided Rope
Some braided ropes are sold with a nominal diameter of 3/16 inch.
That is about 4.76 mm thick.
Rope can compress, and its actual diameter can vary slightly depending on the material and construction, so this should be treated as a nominal comparison.
7. 3/16-Inch Winch Cable
Small winch cables and wire ropes can also come in a 3/16-inch diameter.
That gives them a nominal thickness of 4.7625 mm.
As with rope, the real measured diameter may vary slightly because of manufacturing tolerances and cable construction.
8. Clear Tubing With a 3/16-Inch Opening
Some clear plastic tubing has an inside diameter of 3/16 inch.
The opening through the middle is therefore about 4.76 mm wide.
The outside of the tube will be larger because the tube walls add extra thickness.
9. 5 mm Acrylic Sheet
A 5 mm acrylic sheet is slightly thicker than 3/16 inch.
The difference is only 0.2375 mm, so the two sizes look very similar to the eye.
Some sellers may describe 5 mm acrylic as close to 3/16 inch, but it is not an exact match.
10. About Six Plastic Cards Stacked
A standard plastic bank or ID card is about 0.76 mm thick.
Six cards stacked together would be around:
6 × 0.76 = 4.56 mm
That is about 0.20 mm thinner than 3/16 inch.
Card thickness can vary slightly, so this is only an approximate visual comparison.
Is 3/16 Inch the Same as 5 mm?
No. 3/16 inch is slightly smaller than 5 mm.
| Size | Millimetres |
|---|---|
| 3/16 inch | 4.7625 mm |
| 5 mm | 5.0000 mm |
| Difference | 0.2375 mm |
For a quick visual estimate, you can think of 3/16 inch as being close to 5 mm.
For precision work, the difference can matter. Drill bits, bearings, fasteners, hex keys, and machine parts may need the exact size.
A 5 mm tool or part should therefore not automatically be treated as an exact replacement for a 3/16-inch one.
How to Convert 3/16 Inch to Millimetres
To convert inches to millimetres, multiply the inch value by 25.4.
Start by changing 3/16 into a decimal:
3 ÷ 16 = 0.1875
Then multiply:
0.1875 × 25.4 = 4.7625 mm
So:
3/16 inch = 4.7625 mm
The same method works for any fractional inch measurement once you convert the fraction to a decimal.
3/16 Inch Compared to Nearby Sizes
3/16 inch sits between several common fractional-inch measurements.
| Inch Size | Millimetres |
|---|---|
| 1/8 in | 3.175 mm |
| 5/32 in | 3.96875 mm |
| 3/16 in | 4.7625 mm |
| 7/32 in | 5.55625 mm |
| 1/4 in | 6.35 mm |
1/8 inch is smaller than 3/16 inch by 1.5875 mm.
1/4 inch is larger than 3/16 inch by the same amount.
This means 3/16 inch is exactly halfway between 1/8 inch and 1/4 inch.
It is also slightly larger than 5/32 inch and slightly smaller than 7/32 inch.
Final Thoughts
3/16 inch equals exactly 4.7625 mm, or about 4.76 mm.
An easy way to picture it is as a size just under 5 mm, similar to the diameter of a 3/16-inch drill bit, small dowel, rivet, or bearing ball.
Common Questions
What Is 3/16 Inch in mm?
3/16 inch is exactly 4.7625 mm.
For everyday use, it is usually rounded to 4.76 mm.
Is 3/16 Inch Close to 5 mm?
Yes. 3/16 inch is only 0.2375 mm smaller than 5 mm.
They look very similar, but they are not exactly the same size.
Is 3/16 Bigger Than 1/8 Inch?
Yes. 3/16 inch is larger than 1/8 inch.
3/16 inch equals 4.7625 mm, while 1/8 inch equals 3.175 mm.
Is 3/16 Smaller Than 1/4 Inch?
Yes. 3/16 inch is smaller than 1/4 inch.
1/4 inch equals 6.35 mm, which is 1.5875 mm larger than 3/16 inch.
What Is 3/16 Inch as a Decimal?
3/16 inch is 0.1875 inch in decimal form.
You get this by dividing 3 by 16.
What Metric Size Is Closest to 3/16 Inch?
5 mm is the closest common whole-millimetre size to 3/16 inch.
However, 5 mm is still 0.2375 mm larger than the exact 3/16-inch measurement.
What Size Drill Bit Is 3/16 Inch in Millimetres?
A 3/16-inch drill bit has a nominal diameter of 4.7625 mm.
A 5 mm drill bit is slightly larger, so it should not always be used as an exact substitute.
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