20 inches equals 508 millimeters.
To convert inches to millimeters, you multiply the number of inches by 25.4, since there are exactly 25.4 millimeters in one inch. So, 20 inches times 25.4 millimeters per inch gives 508 millimeters.
Conversion Tool
Result in mm:
Conversion Formula
The formula to convert inches (in) to millimeters (mm) uses the exact relationship that 1 inch equals 25.4 millimeters. To convert, multiply the inch value by 25.4.
This works because the inch and millimeter are units of length in different measurement systems, imperial and metric respectively. The millimeter is much smaller than an inch, so multiplying converts the larger unit to the smaller unit.
Example: Convert 20 inches to millimeters step-by-step:
- Start with 20 inches.
- Multiply 20 by 25.4 (since 1 in = 25.4 mm).
- 20 × 25.4 = 508.
- Therefore, 20 inches equals 508 millimeters.
Conversion Example
- Convert 15 inches to millimeters:
- Start with 15 inches.
- Multiply 15 by 25.4 to get millimeters.
- 15 × 25.4 = 381.
- So, 15 inches equals 381 mm.
- Convert 7.5 inches to millimeters:
- Start with 7.5 inches.
- Multiply 7.5 by 25.4.
- 7.5 × 25.4 = 190.5.
- 7.5 inches equals 190.5 mm.
- Convert 30 inches to millimeters:
- Start with 30 inches.
- Multiply 30 by 25.4.
- 30 × 25.4 = 762.
- 30 inches equals 762 mm.
- Convert 2.25 inches to millimeters:
- Start with 2.25 inches.
- Multiply 2.25 by 25.4.
- 2.25 × 25.4 = 57.15.
- 2.25 inches equals 57.15 mm.
- Convert 40 inches to millimeters:
- Start with 40 inches.
- Multiply 40 by 25.4.
- 40 × 25.4 = 1016.
- 40 inches equals 1016 mm.
Conversion Chart
| Inches (in) | Millimeters (mm) |
|---|---|
| -5.0 | -127.0 |
| -2.5 | -63.5 |
| 0.0 | 0.0 |
| 2.5 | 63.5 |
| 5.0 | 127.0 |
| 7.5 | 190.5 |
| 10.0 | 254.0 |
| 12.5 | 317.5 |
| 15.0 | 381.0 |
| 17.5 | 444.5 |
| 20.0 | 508.0 |
| 22.5 | 571.5 |
| 25.0 | 635.0 |
| 27.5 | 698.5 |
| 30.0 | 762.0 |
| 32.5 | 825.5 |
| 35.0 | 889.0 |
| 37.5 | 952.5 |
| 40.0 | 1016.0 |
| 42.5 | 1079.5 |
| 45.0 | 1143.0 |
This chart shows inches values from negative five to forty-five, converted to millimeters by multiplying every inch value by 25.4. You can read across from the left column to the right for the equivalent millimeters. Use this to quickly find mm values without calculating.
Related Conversion Questions
- How many millimeters are in 20 inches exactly?
- What is 20 in converted to mm with decimal precision?
- Can you convert 20 inches to millimeters for me?
- How do I change 20 in into mm manually?
- What’s the formula to convert 20 inches into millimeters?
- Is 20 inches bigger or smaller than 500 millimeters?
- How do I calculate 20 in to mm using a calculator?
Conversion Definitions
in: An inch is a unit of length measurement in the imperial system, mostly used in the United States. One inch equals exactly 2.54 centimeters or 25.4 millimeters. Inches measure small distances or sizes, such as screen dimensions or building materials.
mm: A millimeter is a metric unit of length, equal to one thousandth of a meter. It is used to measure very small distances or thicknesses with precision, common in engineering, manufacturing, and science. One millimeter equals 0.03937 inches approximately.
Conversion FAQs
Why do we multiply inches by 25.4 to get millimeters?
Because 1 inch is defined as exactly 25.4 millimeters, multiplying the inch value by 25.4 converts the measurement from imperial to metric units. This conversion factor is internationally accepted and does not vary.
Can I convert inches to millimeters without a calculator?
You can estimate by knowing 1 inch is about 25 millimeters, but for precise values like 20 inches, multiplying by 25.4 is needed. This can be done using paper and pencil or a simple calculator.
What happens if I use a rounded factor like 25 instead of 25.4?
Using 25 instead of 25.4 gives approximate results that are slightly smaller. For 20 inches, that would result in 500 mm instead of 508 mm, creating error especially in precise measurements.
Are negative inch values allowed in conversions?
Yes, negative values represent lengths in the opposite direction or below a reference point. The conversion process is the same; multiply the negative inch value by 25.4 to get a negative millimeter result.
Is the conversion factor 25.4 exact or approximate?
The value 25.4 millimeters per inch is exact by international agreement, not an approximation. It standardizes measurement conversions across various fields and countries.