Millimeters, Inches (Fractions), and Centimeters Conversion: The Ultimate Tools & Screws Guide
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Convert Inches to Centimeters (in to cm): The Complete Guide
Whether you’re a DIY enthusiast measuring screws, an online shopper checking screen sizes, or deciphering an assembly manual, knowing how to convert inches to centimeters is an essential skill. The inch (symbol “in” or ″) is the standard unit in the United States, while the centimeter (cm) is the metric system unit used in most other countries.
Confusion between these two systems can quickly lead to costly mistakes. Fortunately, the conversion is simple.
This complete guide provides the exact formula, quick conversion tables, and practical tips to help you master inch-to-centimeter conversions (or inches to cm) for all your projects.
The Essential Conversion Formula: Inches ↔ Centimeters
The golden rule is simple and universal. Every conversion between inches and centimeters relies on this formula:
1 Inch = 2.54 Centimeters (cm)
This is the exact value. With this base, you can calculate anything:
-
To convert inches to centimeters: Multiply your inch value by 2.54.
- Example: 10 in × 2.54 = 25.4 cm
-
To convert centimeters to inches: Divide your centimeter value by 2.54 (or multiply by 0.3937).
- Example: 50 cm ÷ 2.54 = 19.685 in
Quick Conversion Table: Inches to Centimeters (in → cm)
To save time, here’s a conversion table for the most common values — perfect for quick reference without a calculator.
| Inches (in) | Centimeters (cm) |
|---|---|
| 1/4 in (0.25) | 0.635 cm |
| 1/2 in (0.5) | 1.27 cm |
| 3/4 in (0.75) | 1.905 cm |
| 1 in | 2.54 cm |
| 2 in | 5.08 cm |
| 3 in | 7.62 cm |
| 4 in | 10.16 cm |
| 5 in | 12.70 cm |
| 6 in | 15.24 cm |
| 8 in | 20.32 cm |
| 10 in | 25.40 cm |
| 12 in (1 foot) | 30.48 cm |
| 15 in | 38.10 cm |
| 20 in | 50.80 cm |
| 30 in | 76.20 cm |
| 40 in | 101.60 cm |
Conversion Table: Millimeters (mm) to Fractional Inches (Tools & DIY)
In the fields of DIY, mechanics, or plumbing, you often need to match metric sizes (usually in millimeters) to fractional inch sizes (1/4", 3/8", etc.). This is common for wrenches, sockets, or pipe diameters.
Here’s a quick reference table showing the most common metric values and their closest fractional inch equivalents.
| Millimeters (mm) | Fractional Inch (Common Use) |
|---|---|
| 2 mm | ~ 5/64" |
| 3 mm | ~ 1/8" |
| 4 mm | ~ 5/32" |
| 5 mm | ~ 3/16" |
| 6 mm | ~ 1/4" |
| 8 mm | ~ 5/16" |
| 10 mm | ~ 3/8" |
| 12 mm | ~ 1/2" (close to 15/32") |
| 13 mm | ~ 1/2" |
| 15 mm | ~ 5/8" (close to 19/32") |
| 17 mm | ~ 11/16" |
| 19 mm | ~ 3/4" |
| 21 mm | ~ 13/16" |
Practical Example: Why Convert Inches to cm for Furniture (e.g., IKEA)?
Although many international brands like IKEA mainly use the metric system (cm and mm) in their assembly manuals worldwide, you may still come across measurements in inches.
This can happen in several situations:
- Buying from a foreign website: If you purchase accessories for your furniture from a U.S. site, dimensions (screws, handles, etc.) will most likely be in inches.
- Parts compatibility: Need to replace a screw? Metric screws (M4, M5) are not interchangeable with imperial ones (1/4", 5/16"). Knowing how to convert is essential to find the right replacement part.
- Space planning: Found a furniture project on an American IKEA hack blog? The dimensions will be in inches. You’ll need to convert them to centimeters to make sure it fits your space.
In these situations, conversion is crucial to ensure that parts fit properly, screws match, and the final piece of furniture fits perfectly in your intended space.
Online Tools to Convert Inches to Centimeters
If you don’t want to do the math manually, plenty of free online tools can handle it instantly:
- Google: The fastest method. Simply type “10 inches in cm” directly into the search bar.
- UnitConverters.net: A popular unit converter that supports dozens of measurement types.
- Metric-Conversions.org: Another reliable and comprehensive tool for all kinds of unit conversions.
Conclusion: Master Conversion for Error-Free Projects
Whether for a quick calculation or a complex DIY project, knowing how to convert inches to centimeters is a fundamental skill. Remember the magic formula: 1 inch = 2.54 cm.
With this rule, the conversion tables in this article, and online tools, you now have everything you need to move between measurement systems confidently and accurately — avoiding costly assembly or purchasing mistakes.