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1.0 inch is equal to 25.4 millimeters.
The inch is converted to millimeters by multiplying the inch value by 25.4, because one inch is defined exactly as 25.4 millimeters in the international system. This conversion allows precise measurement changes between imperial and metric units.
Table of Contents
Conversion Tool
Result in mm:
Conversion Formula
The formula to convert inches to millimeters is:
millimeters = inches × 25.4.
This formula works because 1 inch is exactly 25.4 millimeters by international agreement. Multiplying the inch value by 25.4 scales the measurement to metric units.
Example calculation for 1.0 inch:
1.0 inch × 25.4 = 25.4 millimeters.
Conversion Example
- 2.5 inches to mm:
- Multiply 2.5 by 25.4.
- 2.5 × 25.4 = 63.5 mm.
- So, 2.5 in = 63.5 mm.
- 0.75 inches to mm:
- Multiply 0.75 by 25.4.
- 0.75 × 25.4 = 19.05 mm.
- Therefore, 0.75 in equals 19.05 mm.
- 10 inches to mm:
- Multiply 10 by 25.4.
- 10 × 25.4 = 254 mm.
- Thus, 10 in is 254 mm.
- 5.25 inches to mm:
- Multiply 5.25 by 25.4.
- 5.25 × 25.4 = 133.35 mm.
- So, 5.25 in equals 133.35 mm.
- 0.1 inches to mm:
- Multiply 0.1 by 25.4.
- 0.1 × 25.4 = 2.54 mm.
- Hence, 0.1 in is 2.54 mm.
Conversion Chart
| Inches (in) | Millimeters (mm) |
|---|---|
| -24.0 | -609.6 |
| -20.0 | -508.0 |
| -16.0 | -406.4 |
| -12.0 | -304.8 |
| -8.0 | -203.2 |
| -4.0 | -101.6 |
| 0.0 | 0.0 |
| 2.0 | 50.8 |
| 6.0 | 152.4 |
| 10.0 | 254.0 |
| 14.0 | 355.6 |
| 18.0 | 457.2 |
| 22.0 | 558.8 |
| 26.0 | 660.4 |
The chart shows inch values in the left column with their equivalent millimeter values on the right. To use it, locate the inch value, then read across to find how many millimeters it equals based on multiplying by 25.4.
Related Conversion Questions
- How many millimeters make up 1.0 inch?
- What is the exact length of 1.0 in in millimeters?
- Can I convert 1.0 inch to mm without a calculator?
- Is 1.0 inch greater than 25 mm or less?
- Why is 1.0 in equal to 25.4 mm and not 25 mm?
- How to convert 1.0 in to mm by hand?
- What is the formula to change 1.0 inch into millimeters?
Conversion Definitions
in (inch): The inch is a unit of length in the imperial and US customary systems, equal to exactly 25.4 millimeters. It is commonly used in the United States, Canada, and the UK for measuring small lengths and distances, especially in construction, manufacturing, and daily life.
mm (millimeter): The millimeter is a metric unit of length equal to one thousandth of a meter. It is widely used worldwide for precise measurements in engineering, manufacturing, and science. The millimeter is part of the International System of Units (SI).
Conversion FAQs
Is the inch to millimeter conversion always exact?
Yes, the conversion between inches and millimeters is exact because 1 inch is defined by international agreement as exactly 25.4 millimeters. This exactness means any inch measurement can be precisely converted to millimeters with no rounding error at the definition level.
Why does 1 inch equal 25.4 millimeters?
The inch was standardized to 25.4 millimeters in 1959 by an international agreement among English-speaking countries. This standardization simplifies trade and manufacturing by providing a fixed conversion factor between imperial and metric length units.
Can I convert negative inches to millimeters?
Yes, negative inch values represent lengths in the opposite direction or below a reference point. The conversion formula still applies, so you multiply the negative inch value by 25.4 to get the corresponding negative millimeter value.
How do I convert fractional inches to millimeters?
To convert fractional inches, first convert the fraction to a decimal, then multiply by 25.4. For example, 1/2 inch is 0.5 inches, so 0.5 × 25.4 = 12.7 mm.
Is millimeter or inch better for precision?
Millimeters generally offer better precision for small measurements because the metric system is decimal-based, making calculations and subdivisions easier. Inches can be divided but often require fractions, which are less straightforward than decimals.
