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If you want to convert 8mm to inches, the answer is 0.31496 inches. This is about 0.315 inches. As a fraction, 8mm is closest to 5/16 inch.
Millimeters and inches are common units of length. Millimeters belong to the metric system, while inches and feet belong to the imperial system.
This guide explains how to convert 8mm to inches, find its closest fraction, read it on a ruler, and use a millimeter-to-inches chart. It also covers other useful size conversions.
How Many Inches Is 8mm?
8 millimeters equals 0.31496 inches.
Here is the quick conversion:
| Millimeters | Inches |
| 8mm | 0.31496 |
| 8mm rounded | 0.315 |
| 8mm as a fraction | 5/16 inch (nearest 1/16) |
So, 8mm converted to inches is about 0.315 inches.
8mm to Inches Fraction
The closest common fraction to 8mm is 5/16 inch.
Here is how 8mm compares with common inch fractions:
| Inch Fraction | Decimal Inches | Millimeters |
| 1/4 inch | 0.2500 | 6.35mm |
| 5/16 inch | 0.3125 | 7.9375mm |
| 3/8 inch | 0.3750 | 9.525mm |
| 1/2 inch | 0.5000 | 12.7mm |
8mm equals 0.31496 inches. It is very close to 5/16 inch, but they are not exactly equal.
How to Convert 8mm to Inches in Fractions
To convert 8mm to inches in fractions, first change it to a decimal.
8 ÷ 25.4 = 0.31496 inches
The nearest common fraction to the nearest 1/16 inch is 5/16.
- 8mm = 0.31496 inches
- 5/16 inch = 0.3125 inches
The difference is very small. You can use 5/16 inch for a simple estimate, but use the decimal value for exact work.
How to Convert 8mm to Inches
You can convert millimeters to inches with this simple formula:
Inches = Millimeters ÷ 25.4
One inch equals 25.4 millimeters.
For 8mm:
8 ÷ 25.4 = 0.31496 inches
This formula works for any millimeter measurement. You can also use an online length conversion calculator.
How to Convert 8mm to Inches on a Ruler
You can find 8mm on both metric and inch rulers.
- On a metric ruler, 8mm is two small marks before the 1cm mark.
- On an inch ruler, 8mm is about 0.315 inches.
- It is slightly more than 1/4 inch.
- It is very close to 5/16 inch.
Use a ruler, measuring tape, or digital caliper when you need an accurate measurement.
8mm to CM
To convert millimeters to centimeters, divide the value by 10.
8 ÷ 10 = 0.8cm
So, 8mm equals 0.8cm.
Do not confuse 8mm with 0.8mm. These are two different measurements.
How Big Is 8mm?
8mm is less than one centimeter. It is about 0.315 inches long and close to 5/16 inch.
Here are some quick facts:
- 8mm = 0.8cm
- 8mm = 0.31496 inches
- 8mm is less than 1cm.
- 8mm is slightly larger than 1/4 inch.
How Thick Is 8mm in Inches?
An object that is 8mm thick is about 0.315 inches thick.
This size may be used for glass, wood, plastic, metal parts, and jewelry beads.
For exact work, check the thickness with a ruler or digital caliper.
MM to Inches and Feet
You can convert millimeters into inches and feet with two simple formulas.
- Millimeters to inches: Divide by 25.4.
- Millimeters to feet: Divide by 304.8.
For example:
| Measurement | Inches | Feet |
| 8mm | 0.31496 | 0.02625 |
| 10mm | 0.39370 | 0.03281 |
| 100mm | 3.93701 | 0.32808 |
| 304.8mm | 12 | 1 |
One foot equals 12 inches or 304.8 millimeters.
MM to Inches Chart
Use this millimeter-to-inches chart to find common measurements.
| Millimeters | Inches (Approx.) |
| 0.8mm | 0.0315 |
| 3mm | 0.1181 |
| 4.8mm | 0.1890 |
| 5mm | 0.1969 |
| 6mm | 0.2362 |
| 7mm | 0.2756 |
| 8mm | 0.3150 |
| 9mm | 0.3543 |
| 10mm | 0.3937 |
| 12mm | 0.4724 |
| 14mm | 0.5512 |
| 16mm | 0.6299 |
| 18mm | 0.7087 |
| 20mm | 0.7874 |
This chart makes it easy to convert millimeters to inches without doing the math each time.
0.8mm to Inches
0.8mm equals 0.031496 inches. Rounded to four decimal places, it is 0.0315 inches.
Its closest common fraction to the nearest 1/16 inch is 1/32 inch.
Remember, 0.8mm is not the same as 8mm. An 8mm measurement is ten times larger.
10mm to Inches Fraction
10mm equals 0.3937 inches.
The closest common fraction to the nearest 1/16 inch is 3/8 inch.
| Measurement | Value |
| 10mm in inches | 0.3937 |
| 3/8 inch in inches | 0.375 |
| 3/8 inch in mm | 9.525mm |
10mm is slightly larger than 3/8 inch. So, 3/8 inch is a close estimate, not an exact match.
4.8mm to Inches Fraction
4.8mm equals 0.18898 inches.
The closest common fraction to the nearest 1/16 inch is 3/16 inch.
- 4.8mm = 0.18898 inches
- 3/16 inch = 0.1875 inches
These measurements are very close but not exactly equal.
3/8 Inch to MM
3/8 inch equals 9.525mm.
To convert inches to millimeters, multiply the inch value by 25.4.
3/8 × 25.4 = 9.525mm
This conversion is useful when comparing inch tools and parts with metric sizes.
Other Common Inch to MM Conversions
You can also convert simple and mixed inch fractions into millimeters.
| Inch Measurement | Millimeters |
| 1/8 inch | 3.175mm |
| 3/8 inch | 9.525mm |
| 5/8 inch | 15.875mm |
| 1 3/8 inches | 34.925mm |
| 1 7/8 inches | 47.625mm |
| 2 3/8 inches | 60.325mm |
| 2 5/8 inches | 66.675mm |
To convert any inch measurement to millimeters, multiply it by 25.4.
Small Millimeter Fractions to Inches
Some measurements use fractions of a millimeter. You can convert them into decimal inches.
| Millimeter Measurement | Decimal Inches |
| 3/8mm | 0.01476 |
| 5/8mm | 0.02461 |
| 0.8mm | 0.03150 |
| 4.8mm | 0.18898 |
| 8mm | 0.31496 |
These are millimeter fractions converted to decimal inches. They are not the same as 3/8 inch or 5/8 inch.
Common Uses of 8mm Measurements
An 8mm measurement is used for many small parts and objects.
8mm Bolt and Nut
An 8mm bolt has a metric size. The number usually refers to the thread diameter. An 8mm nut is made to fit a matching bolt.
8mm Socket and Wrench
An 8mm socket or wrench is used with matching metric fasteners. Do not use a close inch size if the tool does not fit properly.
8mm Drill Bit
An 8mm drill bit has a cutting diameter of 8 millimeters. It is about 0.315 inches and close to a 5/16-inch drill bit.
Glass and Wood Thickness
An 8mm thickness may be used for glass, wood, and other materials. Check the exact size before buying or cutting a material.
Beads and Jewelry
An 8mm bead has a diameter of 8 millimeters. This equals about 0.315 inches and can help when choosing beads for bracelets and necklaces.
Common Mistakes When Converting Measurements
Avoid these mistakes when converting millimeters and inches:
- Using the wrong formula: Divide millimeters by 25.4 to get inches.
- Mixing up mm and cm: 8mm equals 0.8cm, not 8cm.
- Confusing 3/8 inch with 3/8mm: These are very different sizes.
- Treating a close fraction as exact: 8mm is close to 5/16 inch, but not equal.
- Rounding too early: Keep more decimal places when accuracy matters.
FAQs About Converting 8mm to Inches
8mm equals 0.31496 inches, or about 0.315 inches.
8mm is closest to 5/16 inch when rounded to the nearest 1/16 inch.
No. 8mm is 0.31496 inches, while 5/16 inch is 0.3125 inches.
8mm equals 0.8cm.
0.8mm equals 0.031496 inches, or about 0.0315 inches.
10mm equals about 0.3937 inches. Its closest common 1/16-inch fraction is 3/8 inch.
3/8 inch equals 9.525mm.
4.8mm equals about 0.18898 inches. It is closest to 3/16 inch.
Divide the millimeter value by 25.4. For example, 8 ÷ 25.4 = 0.31496 inches.
Multiply the inch value by 25.4. For example, 3/8 × 25.4 = 9.525mm.
Conclusion
8mm equals 0.31496 inches, or about 0.315 inches. Its closest common fraction to the nearest 1/16 inch is 5/16 inch. It also equals 0.8cm and about 0.02625 feet.
Use the formula, conversion chart, or ruler to change millimeters into inches. For exact work, use the decimal value instead of a rounded fraction.
Justin Walker writes clear how-to and explainer articles that break topics into simple steps. He aims for practical, easy-to-follow content, so readers can understand a subject quickly and know exactly what to do next.
