1.5 inches equals 38.1 millimeters.
To convert inches to millimeters, multiply the inch value by 25.4 because one inch is exactly 25.4 millimeters. So, 1.5 inches times 25.4 equals 38.1 millimeters.
Conversion Tool
Result in millimeters:
Conversion Formula
The formula to convert inches into millimeters is simple: millimeters = inches × 25.4. Because one inch equals 25.4 millimeters exactly, multiplying the inches by 25.4 gives the length in millimeters.
Why 25.4? The inch was defined as exactly 25.4 millimeters internationally in 1959 to standardize measurements. So any inch measurement times 25.4 will produce millimeters.
Example calculation for 1.5 inches:
- Start with 1.5 inches
- Multiply by 25.4: 1.5 × 25.4 = 38.1
- Result: 38.1 millimeters
Conversion Example
- Convert 3 inches to millimeters:
- Multiply 3 × 25.4
- Result is 76.2 millimeters
- So, 3 inches equal 76.2 mm
- Convert 0.75 inches to millimeters:
- 0.75 × 25.4 = 19.05
- Therefore, 0.75 inches is 19.05 mm
- Convert 12.3 inches to millimeters:
- Calculate 12.3 × 25.4
- Result: 312.42 millimeters
- So 12.3 inches equals 312.42 mm
- Convert 5.5 inches to millimeters:
- Multiply 5.5 × 25.4
- Result is 139.7 millimeters
- 5.5 inches correspond to 139.7 mm
Conversion Chart
| Inches | Millimeters |
|---|---|
| -23.5 | -23.5 × 25.4 = -596.9 |
| -20.0 | -20.0 × 25.4 = -508.0 |
| -15.5 | -15.5 × 25.4 = -393.7 |
| -10.0 | -10.0 × 25.4 = -254.0 |
| -5.0 | -5.0 × 25.4 = -127.0 |
| 0 | 0 × 25.4 = 0 |
| 5.0 | 5.0 × 25.4 = 127.0 |
| 10.0 | 10.0 × 25.4 = 254.0 |
| 15.0 | 15.0 × 25.4 = 381.0 |
| 20.0 | 20.0 × 25.4 = 508.0 |
| 23.5 | 23.5 × 25.4 = 596.9 |
| 26.5 | 26.5 × 25.4 = 673.1 |
The chart shows inches in the left column and their converted millimeter values on right. Negative values mean measurements below zero, useful for length differences or depths. You can use it to quickly find approximate millimeter equivalents without calculation.
Related Conversion Questions
- How many millimeters are in 1.5 inches exactly?
- What is the formula to convert 1.5 inches into millimeters?
- Is 1.5 inches equal to 38 millimeters or 39 millimeters?
- Can I convert 1.5 inches to millimeters without a calculator?
- How to convert 1.5 inch ruler measurements to millimeters?
- What’s the difference between 1.5 inches and 38 millimeters?
- How much is 1.5 inches in millimeters for engineering purposes?
Conversion Definitions
Inches: An inch is a unit of length used primarily in the United States and UK. It equals exactly 1⁄12 of a foot and is standardized as 25.4 millimeters internationally. Inches measure short distances, often seen in construction, manufacturing, and everyday objects.
Millimeters: A millimeter is a metric unit of length equal to one-thousandth of a meter. It is used worldwide for precise measurements in science, engineering, and manufacturing. Millimeters provide a fine scale for measuring small distances or thicknesses.
Conversion FAQs
Why does multiplying inches by 25.4 convert them to millimeters?
Because one inch is internationally defined as exactly 25.4 millimeters, multiplying by 25.4 converts the unit. This fixed ratio makes the calculation exact without approximation. So when you multiply inches by 25.4, you get millimeters directly.
Can decimal inch values be converted using the same formula?
Yes, decimal and fractional inch values can both be converted the same way. Whether you have 1.5, 2.75, or 0.125 inches, multiplying them by 25.4 gives millimeter equivalents. The formula applies universally to any inch value.
Are there any rounding errors when converting inches to millimeters?
Since one inch equals exactly 25.4 millimeters, the base conversion has no rounding error. However, when you round the result to fewer decimal places, small differences appear. Using more decimal places reduces these rounding effects.
Why use millimeters over inches in some cases?
Millimeters provide finer resolution because they are smaller units. For precision measurements, like in engineering or machining, millimeters help express lengths more accurately. Inches are often used in regions like the US, but metric units are standard worldwide.
Is there a way to convert millimeters back to inches?
Yes, divide millimeters by 25.4 to find inches. Since 1 inch equals 25.4 millimeters, the reverse conversion uses division, allowing easy switching between the two units.
