42 inches is equal to 1066.8 millimeters.
To convert inches to millimeters, multiply the number of inches by 25.4, because one inch equals exactly 25.4 millimeters. So, 42 inches times 25.4 millimeters per inch gives the total millimeters.
Conversion Tool
Result in mm:
Conversion Formula
The formula to convert inches to millimeters is:
millimeters = inches × 25.4
This formula works because one inch equals exactly 25.4 millimeters as per international agreement. So, multiplying the inch value by 25.4 shifts the measurement from imperial units to metric units.
For example, converting 42 inches:
- Step 1: Take the inch value: 42
- Step 2: Multiply by 25.4 (the conversion factor): 42 × 25.4 = 1066.8
- Step 3: The result is 1066.8 millimeters.
Conversion Example
- Convert 30 inches to millimeters:
- Start with 30 inches.
- Multiply 30 × 25.4 = 762.
- The result is 762 millimeters.
- Convert 55.5 inches to millimeters:
- Take 55.5 inches.
- Multiply 55.5 × 25.4 = 1409.7.
- So, 55.5 inches equals 1409.7 millimeters.
- Convert 10 inches to millimeters:
- Value is 10 inches.
- Multiply 10 × 25.4 = 254.
- Result is 254 millimeters.
- Convert 67 inches to millimeters:
- Start with 67 inches.
- Multiply 67 × 25.4 = 1701.8.
- Therefore, 67 inches equals 1701.8 millimeters.
Conversion Chart
The following chart shows selected inch values converted to millimeters. You can use it to quickly find the millimeter equivalent for inches between 17.0 and 67.0 without doing the math.
| Inches | Millimeters (mm) |
|---|---|
| 17.0 | 431.8 |
| 25.0 | 635.0 |
| 33.0 | 838.2 |
| 42.0 | 1066.8 |
| 50.0 | 1270.0 |
| 58.0 | 1473.2 |
| 67.0 | 1701.8 |
Related Conversion Questions
- How many millimeters are in 42 inches exactly?
- What is the formula to convert 42 inches to mm?
- Is 42 inches more or less than 1000 millimeters?
- How to calculate length in mm from 42 inch measurement?
- Why does 42 inches equal 1066.8 mm and not a rounded number?
- Can I convert 42 inches into millimeters without a calculator?
- What is the difference between 42 inches and 42 millimeters in size?
Conversion Definitions
Inch: An inch is a unit of length in the imperial and US customary systems, equal to exactly 1/12 of a foot or 2.54 centimeters. It is used mainly in the United States, Canada, and the United Kingdom for measuring shorter distances, such as in construction, manufacturing, and daily measurements.
Millimeter (mm): The millimeter is a metric unit of length equal to one thousandth of a meter. It is commonly used worldwide in science, engineering, and everyday life for measuring small distances or thicknesses, providing precise measurements in metric system applications.
Conversion FAQs
Why is the conversion factor for inches to millimeters exactly 25.4?
The value 25.4 millimeters per inch was internationally agreed upon in 1959, standardizing measurements between countries using imperial and metric systems. This exact fixed number ensures consistent, accurate conversions across industries and scientific fields.
Can I convert inches to millimeters by just multiplying by 2.5?
Multiplying by 2.5 is only an approximation and gives a rough estimate. The correct factor is 25.4, which is ten times larger. Using 2.5 would cause a big error, so always use 25.4 to get precise results.
Does converting 42 inches to millimeters affect the precision of measurement?
The conversion itself does not reduce precision if done correctly. However, rounding the millimeter result to fewer decimal places may lose some accuracy. For exact work, keep decimal places as needed after multiplying by 25.4.
What tools can help convert inches to millimeters quickly?
Besides manual calculation, online converters, calculator apps, and embedded conversion tools in devices can quickly convert inches to millimeters. The included JavaScript tool above can also perform live conversions in your browser.
Is the inch measurement still relevant when metric is widely used?
Yes, inches remain relevant in countries like the US and UK, especially in construction, manufacturing, and consumer products. While the metric system is widespread globally, some industries prefer inches for certain applications.