1.5 inches is equal to 38.1 millimeters.
To convert inches to millimeters, multiply the length value by 25.4, because one inch equals exactly 25.4 millimeters. Therefore, 1.5 inches times 25.4 gives you the equivalent length in millimeters.
Conversion Tool
Result in mm:
Conversion Formula
The formula for converting inches to millimeters is simple: multiply the inch value by 25.4. This works because one inch is exactly 25.4 mm by international agreement, so the factor 25.4 converts inches directly to millimeters.
Mathematically, it’s:
millimeters (mm) = inches × 25.4
Example calculation for 1.5 inches:
- Start with 1.5 inches
- Multiply 1.5 by 25.4
- 1.5 × 25.4 = 38.1 mm
- So, 1.5 inches equals 38.1 millimeters
Conversion Example
- Convert 3 inches to mm:
- Multiply 3 × 25.4
- 3 × 25.4 = 76.2 mm
- Therefore, 3 inches equals 76.2 mm
- Convert 0.75 inches to mm:
- Multiply 0.75 × 25.4
- 0.75 × 25.4 = 19.05 mm
- This means 0.75 inches equals 19.05 mm
- Convert 12.3 inches to mm:
- Calculate 12.3 × 25.4
- 12.3 × 25.4 = 312.42 mm
- So, 12.3 inches is 312.42 mm
- Convert 5.6 inches to mm:
- Multiply 5.6 × 25.4
- 5.6 × 25.4 = 142.24 mm
- Hence, 5.6 inches equals 142.24 mm
Conversion Chart
This chart shows inch values from -23.5 to 26.5 converted into millimeters. Use it by locating the inch value on the left column, then reading across to find its equivalent in millimeters. Negative values represent lengths measured in the opposite direction.
| Inches | Millimeters (mm) |
|---|---|
| -23.5 | -23.5 × 25.4 = -596.9 |
| -20.0 | -20.0 × 25.4 = -508.0 |
| -15.0 | -15.0 × 25.4 = -381.0 |
| -10.5 | -10.5 × 25.4 = -266.7 |
| -5.0 | -5.0 × 25.4 = -127.0 |
| 0.0 | 0.0 × 25.4 = 0.0 |
| 2.5 | 2.5 × 25.4 = 63.5 |
| 5.0 | 5.0 × 25.4 = 127.0 |
| 7.75 | 7.75 × 25.4 = 196.85 |
| 10.0 | 10.0 × 25.4 = 254.0 |
| 13.2 | 13.2 × 25.4 = 335.28 |
| 17.5 | 17.5 × 25.4 = 444.5 |
| 21.0 | 21.0 × 25.4 = 533.4 |
| 24.0 | 24.0 × 25.4 = 609.6 |
| 26.5 | 26.5 × 25.4 = 673.1 |
Related Conversion Questions
- How many millimeters are in 1.5 inches exactly?
- What is the formula to convert 1.5 inches to mm?
- Is 1.5 inches longer than 38 mm?
- How do I convert 1.5 inches into millimeters manually?
- What’s the difference between 1.5 inches and 38 mm?
- Can 1.5 inches be rounded to 40 mm?
- Why does 1.5 inches equal 38.1 mm instead of 40 mm?
Conversion Definitions
Inches: An inch is a unit of length in the imperial and US customary measurement systems. One inch equals exactly 2.54 centimeters or 25.4 millimeters. It is commonly used in the United States, Canada, and the UK for measuring small distances, screen sizes, and hardware dimensions.
Millimeters: A millimeter is a metric unit of length equal to one thousandth of a meter. It is a standard unit in most countries worldwide, used for precise measurements in engineering, construction, and manufacturing. There are 25.4 millimeters in one inch.
Conversion FAQs
Why is one inch equal to 25.4 millimeters?
The inch was standardized to exactly 25.4 millimeters internationally in 1959 to unify measurement systems. Before this, different countries used slightly different definitions. This fixed value allows easy and accurate conversion between imperial and metric units, avoiding confusion in trade and science.
Can I convert inches to mm without a calculator?
Yes, but it requires memorizing the conversion factor 25.4. You multiply the inches by 25.4 to get millimeters. For rough estimates, you might use 25 or 26 as a multiplier, but it will reduce accuracy. For precise work, a calculator or conversion tool helps.
What happens if I convert a negative inch value to mm?
Negative inches represent a measurement in the opposite direction or below a reference point. When converted, the result is a negative millimeter value. The formula works the same, multiplying by 25.4 but keeping the negative sign, showing relative position or depth.
Is 1.5 inches exactly 38 mm?
No, 1.5 inches equals 38.1 millimeters exactly. Since 1 inch = 25.4 mm, multiplying gives 38.1 mm. The 38 mm figure is rounded down, so it’s slightly less than the true length in millimeters.
How precise is the conversion from inches to mm?
The conversion is exact because 1 inch is defined as exactly 25.4 millimeters by international agreement. Precision depends on how many decimal places you keep after multiplying. For most applications, four decimal places or less is sufficient.