004 inches is equal to 0.1016 millimeters.
The conversion from inches to millimeters is done by multiplying the inch value by 25.4, since one inch equals 25.4 millimeters. Thus, 004 inches when multiplied by 25.4 gives the result in millimeters.
Conversion Tool
Result in mm:
Conversion Formula
To convert inches (in) to millimeters (mm), multiply the inches value by 25.4. This is because there are exactly 25.4 millimeters in one inch, a standard defined internationally. The formula looks like this:
mm = in × 25.4
For example, converting 004 inches:
- Write the value in inches: 004 (which is 4)
- Multiply by 25.4: 4 × 25.4 = 101.6
- The result is 101.6 mm
This formula works since the inch is a unit based on imperial measurement and millimeters are metric, so the fixed ratio allows converting precisely.
Conversion Example
- Example 1: Convert 2.5 in to mm
- Multiply 2.5 × 25.4
- Result: 63.5 mm
- Example 2: Convert 0.75 in to mm
- 0.75 × 25.4 = 19.05 mm
- Example 3: Convert 10 in to mm
- 10 × 25.4 = 254 mm
- Example 4: Convert 0.1 in to mm
- 0.1 × 25.4 = 2.54 mm
- Example 5: Convert 15.6 in to mm
- 15.6 × 25.4 = 396.24 mm
Conversion Chart
The chart below shows values from -21.0 inches up to 29.0 inches converted to millimeters. Use this chart for quick reference when converting inches to mm without calculation. Negative values represent measurements below zero, which might be used in contexts like depth or displacement.
Inches (in) | Millimeters (mm) |
---|---|
-21.0 | -533.4 |
-15.0 | -381.0 |
-10.0 | -254.0 |
-5.0 | -127.0 |
0.0 | 0.0 |
5.0 | 127.0 |
10.0 | 254.0 |
15.0 | 381.0 |
20.0 | 508.0 |
25.0 | 635.0 |
29.0 | 736.6 |
Related Conversion Questions
- How many millimeters are in 004 inches exactly?
- What is the formula to convert 004 in to mm?
- Is 004 inches bigger or smaller than 100 mm?
- Can I convert 004 in to mm using an online calculator?
- What is 004 inches in millimeters rounded to two decimals?
- How do I convert fractional inches like 004 in to millimeters?
- Why does 004 inches equal 101.6 mm in measurements?
Conversion Definitions
In (inch): The inch is a unit of length in the imperial and US customary systems, defined as exactly 25.4 millimeters. It is commonly used in the United States, Canada, and the UK for measuring height, width, and length in various applications, including construction, manufacturing, and tailoring.
Mm (millimeter): The millimeter is a metric unit of length equal to one-thousandth of a meter. It is widely used globally for precise measurements in science, engineering, and everyday life. One millimeter equals 0.03937 inches, making it smaller than the inch unit.
Conversion FAQs
Can I convert 004 inches to millimeters without a calculator?
Yes, you can convert 004 inches to millimeters by multiplying the inch value by 25.4. For example, 004 inches means 4 inches, so 4 × 25.4 equals 101.6 millimeters. You just need to remember the conversion factor 25.4 to do it manually.
Why is the conversion factor exactly 25.4?
The factor 25.4 was internationally agreed upon to precisely define the inch in terms of metric units. This exact value simplifies conversion between the imperial and metric systems, ensuring consistency in measurements worldwide without rounding errors.
Is converting negative inch values to millimeters valid?
Yes, negative values indicate measurements in the opposite direction or below a reference point. When converting negative inches, multiply by 25.4 as usual, and the result will be negative millimeters, maintaining the direction or relative position.
How accurate is converting 004 inches to millimeters?
The conversion is exact because 1 inch equals 25.4 millimeters by definition. Therefore, converting 004 inches (or any inch value) to millimeters is precise, with no approximation needed, unless you round the final result.
Can I convert fractional inches like 0.004 in to millimeters using the same method?
Yes, fractional inches work the same way. Multiply the decimal inch value by 25.4. For 0.004 inches, that’s 0.004 × 25.4 = 0.1016 mm. The method applies to any decimal or fractional inch measurement.
Last Updated : 30 June, 2025


Sandeep Bhandari holds a Bachelor of Engineering in Computers from Thapar University (2006). He has 20 years of experience in the technology field. He has a keen interest in various technical fields, including database systems, computer networks, and programming. You can read more about him on his bio page.